|Radio Paging System Basics|
PAGING SYSTEM OVERVIEW
(Source: Motorola, author unknown.)
1.0 PAGING INTRODUCTION
Two pieces of information that determine the paging message are the individual pager address (cap code) and the actual information to be sent to the pagers. Pager addresses and paging information can exist in two forms, either analog or binary. An analog transmission refers to a paging receiver receiving a signal on the paging transmit carrier frequency and demodulating audio tones or voice transmissions. A binary transmission differs from an analog transmission in the sense that the receiver looks for frequency shifts above and below the carrier and never has to lock on to the transmit carrier frequency. This type of transmission is referred to as Frequency Shift Keying Non Return to Zero, or FSK-NRZ for short. These shifts above and below the carrier correspond with the binary number system of ones and zeros. In this manner we can transmit and receive data based directly on the binary number system. Another parameter of importance for binary transmissions is the information transmission speed, often referred to as the baud rate. The baud rate is typically denoted by units of bits per second, where a bit is a binary one or zero. The greater the baud rate number, the faster the transmission speed and the less system air time needed to transmit the desired paging information.
1.1 ANALOG PAGER ADDRESSING MODES
The 5-Tone/6-Tone Decimal Digit coding format supports tone and voice pagers however this coding format can alert pagers much faster than the Two-Tone coding format. The 5-Tone/6-Tone coding format uses 12 separate frequency tones to represent the decimal digits 0 through 9, a repeat number tone (R), and a special Tone X function. Each pager address is made up of 5 digits represented by the respective frequency tone burst. The tone bursts are sent sequentially, 33 milliseconds in duration each. A sixth tone burst is used for multiple addressing applications, hence the name 5/6 tone signaling. The 5-Tone/6-Tone coding format can support 100,000 subscribers. A typical 5/6 tone page takes approximately .217 seconds to alert the pager, a 12 times improvement over a standard Two-Tone page of 2.5 seconds.
1.2 BINARY ADDRESSING AND DATA CODING FORMATS
The POCSAG coding format was primarily invented to improve signaling speed thereby increasing system throughput. The POCSAG coding format has an increased code capacity of 2 million codes with 4 addresses per pager. Unlike GSC which is asynchronous, POCSAG employs bit synchronization and word framing. POCSAG uses time division for battery saver operation whereas GSC relies on selective batching. POCSAG signaling operates with both address and data at the same baud rate, initial offering at 512 baud. Improvements in equipment technology have increased the POCSAG signaling speed to 1200 and 2400 baud. At a 512 baud rate POCSAG address alerts take .0625 seconds. This a 3 times improvement over the GSC signaling scheme. The structure of the POCSAG coding format allows for substantial system throughput performance. It is, however less immune to falsing than GSC signaling. POCSAG can correct 2 of 32 bits for address words and 1 of 32 for data words, whereas GSC can correct 3 of 23 bits for address words and 16 of 120 bits for data words. Depending on the desired system capacity, throughput, coverage and immunity noise the system operator can decide which binary code format best suits there needs. More detailed information regarding analog and binary coding formats can be found in Motorola PAGING FORMAT GUIDE publication # TBD.
1.3 PAGING SYSTEM TYPES: NON-SIMULCAST vs. SIMULCAST
A Simulcast Paging system refers to a system where coverage is continuous over a geographic area serviced by more than one paging transmitter. In this type of system the pager can be receiving signals from two or more paging transmitters when in the overlap area of the two or more paging transmitter. The overlap are of two or more paging transmitters is referred to as the non-capture are since a pager not locked or captured by a single transmitter. The construction of Simulcast System takes advantage of the overlapping transmitters signals in a constructive manner so that coverage is improved and the system can provide continuous coverage over a wide geographic area. This is accomplished during system optimization by delaying the signals from the transmitters that have overlapping coverage such that the signal arrives at the same time in the overlap area. This delay criterion is of great importance for binary paging. For analog paging additional signal qualities of phase and gain must be optimized for overlapping transmitters. A properly designed and optimized simulcast system will utilize the effects of overlapping transmitters to improve coverage and ensure that the audio and binary transmissions from all transmitters are of the highest possible quality and the signals arrive in the overlap area at exactly the same time from the pagers point of view. These Simulcast system constraints therefore dictate the transmitter hardware to be more precise and of tighter tolerance from one transmitter to the other. The frequency band and type of paging supported by the system will determine the amount of transmitter stability required reflected in additional transmitter hardware and cost. With the Simulcast System comes the need for increased system monitoring for changes and the ability of the system to compensate for changes that will degrade performance.
1.4 SECTOR PAGING
1.5 MULTIPLE FREQUENCY PAGING
1.6 PAGING SYSTEM BLOCK DIAGRAM AND COMPONENTS
FIGURE 1. Paging System Block Diagram
OPERATIONAL DESCRIPTION OF THE 6 BASIC PAGING SYSTEM ELEMENTS
1) THE PAGING TERMINAL
2) THE CONTROLLER
3) THE OUTBOUND CONTROL AND PAGING INFORMATION CHANNEL
4) TRANSMITTER NETWORK
5) COMMUNICATIONS LINK
BASE STATION CONTROL METHODS
2.0 TONE REMOTE CONTROL
Paging uses a Tone Remote Control sequence called PURC TRC. PURC is an acronym for Paging Universal Remote Control. The above mentioned TRC sequence was modified and redefined to allow for keying a transmitter on a specific frequency channel as well as putting the transmitter in the proper mode of operation, analog or binary. The mode of transmitter operation is determined by the information which follows the TRC sequence. The analog mode is assumed when the normal TRC sequence of HLGT, FT, and LLGT is sent. The binary mode of operation is entered when no LLGT follows the FT, but instead a gap or pause of silence occurs followed by paging modem tones. The detection of silence can sometimes be falsed on a noisy control channel thereby making mode switches from analog to binary not possible. Consequently the binary page goes out in the analog mode and the pager is not alerted.
HLGT is a 2175 Hz. frequency tone which indicates the start of a TRC control sequence. Function Tone is used to tell the transmitter on what frequency channel to key or is used to disable a transmitter when sector paging is used. FT values range from 750 Hz. to 2350 Hz. in 100 Hz. steps. The 1950 Hz. function tone is the standard key on channel 1 frequency. LLGT is a 2175 Hz. tone used to let the base station know that the controller has access of the channel in the analog mode. A loss of LLGT and activity by the base station for more than 350 milliseconds will cause the transmitter to drop off the air. For more in depth timing information on the operation of PURC TRC consult the PURC Simulcast System Controller and Paging Station Controller instruction manual, part number 6881063E15.
Non-Simulcast Function Tone Key Commands for PURC 5000 stations. This option requires special TRC software and the transmitter needs to be programmed for multiple frequency operation.
Simulcast Station Function Tone Key Commands Standard PURC 5000 station TRC.
FIGURE 2. PURC Tone Remote Control Audio Flow Diagram
2.1 DIGITAL REMOTE CONTROL
Unlike TRC, which had limited control functionality, DRC is able to transfer much more information in each transmitted packet of MDC 1200. Due to error detection and correction, DRC offers substantial reliability in performance over TRC in noise environments. Unlike TRC which relied on "pauses" and "gaps" of silence to force mode switches, DRC simply sends a specific message identifying the desired mode of operation. DRC is therefore referred to as a positive control scheme. See Figure 3 and 4 below which illustrate Analog and Binary DRC keying sequences. The sequences shown are for single key and de-key modes. If multiple and alternating key requests were present the de-key message would be substituted with the appropriate MDC keying message. HLGT does not need to be resent since the link will remain keyed on activity.
ORIGINAL DRC CONTROL INFORMATION FLOW AND RELATIVE LEVEL DIFFERENCES
FIGURE 3. Analog and Binary keying sequence for Non-Advanced Control DRC Paging Stations
Figure 3 illustrates the order of control information as well as relative level differences in the information. As shown above HLGT is only required for a RF control system. HLGT is used for keying link transmitters and repeaters. The duration of HLGT is dependent on the number of repeaters and if DPL is used or not. See the section on page RF Distribution Channel for details. The MDC DRC messages are sent at the same level as HLGT. LLGT is sent only during an analog page as a positive qualifier for being in the analog mode. The base station looks for LLGT and will drop off the air if LLGT is not detected for more than 6 seconds and no audio activity exists. This is required as a fail safe in the event of a control channel impairment to the station, i.e. receiver, link transmitter, or link repeater failure, prior to decoding an MDC de-key message. With out this fail safe the station could remain keyed indefinitely with dead or offset carrier. LLGT is transmitted 30 dB down from HLGT and MDC audio level. The base station will notch filter the LLGT signal another 30-40 dB to prevent the tone from mixing with a voice page and degrading the audio quality. For an Analog transmission the audio is sent at 5 dB down from HLGT and MDC audio level. For a binary page LLGT is not sent. After a binary key message, FSK modem tones are sent until no more binary pages exist. The station senses FSK audio and will drop off the air if FSK audio is not detected for more than 6 seconds. This check of incoming FSK audio is a fail safe to prevent a transmitter from being keyed indefinitely if the control channel to the station is impaired, i.e. receiver, link transmitter, or link repeater failure, prior to decoding an MDC de-key message. The FSK modem tones are sent 5 dB down from HLGT and MDC audio level.
ADVANCED CONTROL DRC INFORMATION FLOW AND RELATIVE LEVEL DIFFERENCES
FIGURE 4. Analog and Binary keying sequence for Advanced Control DRC Paging Stations
Advanced Control Paging Stations are designed with a different hardware and software architecture than non-advanced control paging stations. This architecture difference imposes some operating differences in the MDC audio level required for optimal station MDC decoding. The only difference between Figure 3 and Figure 4 is the MDC message level relative to HLGT and paging information audio. MDC audio is 5 dB below HLGT. MDC audio level now is at the same level as either analog or binary paging information. In the event a DDC controller is used with Advanced Control Paging Stations, the MDC audio level from the Digital Diagnostic Controller (DDC) should be decreased by 5 dB. This 5 dB reduction in level gives the station additional high end head room. Non-Advanced control stations working under this audio level protocol will be more susceptible to falsing low deviation alarms since the alarm trip point is fixed in hardware and will alarm when MDC is received at 6 dB below the HLGT level. This only gives the channel 1 dB of margin as opposed to 6 dB.
2.2 DRC MESSAGE STRUCTURE AND FORMAT TYPES
2.3 DRC 1
To better understand DRC 1 communications for key control and diagnostic messaging the following three DRC parameters must be discussed, namely, the System ID, the Group ID, and the Individual Station ID. The System ID has 255 possible values, ranging from 0 to 254. The System ID uniquely associates a paging transmitter with a DRC controller. The controller and paging transmitter must be programmed with matching System ID's if they are to communicate. Key control for paging is based on the System ID alone.
The Group ID is another ID used to differentiate the controller from the base station. The Group ID has 1024 possible values, ranging from 0 to 1023. The Group ID was implemented early on in the DRC development program for potential future expansion, however it has never been utilized. The Group ID is set by hardware jumpers on the DRC CPB board, unlike the System ID which is programmed in EEPROM non-volatile memory. A peculiarity between the Group ID and DDC controller does exist however. During diagnostic messaging, the station responses include the status of the CPB board Group ID. If the Group ID does not match the Group ID programmed in the DDC, then the message is ignored. This often creates a problem when someone accidentally changes the DDC Group ID value and then cannot figure out why the station keys and sends diagnostic messages but the controller reports a No Response alarm. The CPB board ships from the factory with a Group ID of 0 and should never be changed. For the Advanced Control, ASC 1000, and ASC 1500 product, the Group ID is not a changeable value and defaults to 0. The Group ID concept has been canceled in these new products. When upgrading system equipment be sure the paging transmitters have group ID's of 0 so that diagnostic messaging is possible with these new products.
The Individual Station ID is used to uniquely assigns an ID to each paging transmitter so that they can be communicated with individually by the controller. The Individual Station ID has 1024 values, ranging from 0 to 1023. The ID is set locally at the paging transmitter during installation. Care must be taken not to assign two stations with the same Individual Station ID since diagnostic messaging will not be possible for both transmitters. The Individual Station ID has no bearing on paging key-ups, only diagnostic or individual station testing key-ups.
The DRC 1 format has provisions for transmitter keying on up to 4 frequencies and 254 sectors, for both the analog and binary paging modes and transmitter test modes. The DRC 1 message format allows for the following paging transmitter diagnostic messaging, forward and reflected power readings, delay line setting, station audio gain and inversion, station frequency adjust, wild card input reads, and wild card output writes, and level 1 alarm information. Level 1 alarms are specific to the PURC 5000 paging transmitter alarm set and include, Tx fault, PA fault, synthesizer out of lock, low deviation, battery revert, system timer, external 1, and external 2 alarms. For Micor DRC stations all diagnostic messaging and alarms apply except for the station frequency adjust capability and PA fault alarm.
2.4 DRC 2
To better understand DRC 1 communications for key control and diagnostic messaging the following two DRC parameters must be discussed, namely, the System ID, and the Individual Station ID. The System ID has 16 possible values, ranging from 0 to 15. The System ID uniquely associates a paging transmitter with an ASC 1500 DRC controller. The controller and paging transmitter must be programmed with matching System ID's if they are to communicate. Key control for paging is based on the System ID alone. As mentioned in the DRC 1 section, the Group ID parameter has been canceled for DRC 2 messaging. When converting a system from DDC or ASC 1000 controller operation to ASC 1500 controller, the system ID must be with in the 0 to 15 range. Use the original controller to change the station System ID to a value between 0 and 15.
The Individual Station ID is used to uniquely assign an ID to each paging transmitter so that they can be communicated with individually by the controller. The Individual Station ID has 1024 values, ranging from 0 to 1023. The ID is set locally at the paging transmitter during installation. Care must be taken not to assign two stations with the same Individual Station ID since diagnostic messaging will not be possible for both transmitters. The Individual Station ID has no bearing on paging key-ups, only diagnostic or individual station testing key-ups.
The DRC 2 format has provisions for transmitter keying on up to 4 frequencies and 254 sectors, for both the analog and binary paging modes and transmitter test modes. The DRC 2 message format can support all alarm and diagnostic information provided by DRC 1 messaging however it is communicated in a much more efficient manner. The DRC 2 format allows for new messaging required for Advanced Control and ASC 1500 systems which could never be implemented with the DRC 1 format.
2.5 KEY ON DATA
2.6 DIRECT DIGITAL CONTROL
Direct Digital Control is currently used for digital satellite distribution channels. The ASC 1500 and Advanced Control paging stations are required for this type of system operation. The ASC transmits MDC in digital form at 1200 baud and then passes or generates paging terminal data in the digital form as well. The ASC when used to pass terminal data, expects data from the terminal at RS 232 levels and outputs the data at RS 232 levels. Pass through digital transmissions are restricted to baud rates of 300, 600, and 1200. The ASC when used with an MPS 2000 terminal can be configured to generate the paging information. In this manner the ASC acts like the terminal output card. Paging data is user selectable for TTL or RS 232 output levels. The ASC also provides handshake signals, Request-To-Send (RTS) and CTS-To-Send (CTS), to be used for interface with the external Digital transmission equipment for the satellite uplink.
CONTROL AND PAGING INFORMATION CHANNEL
3.0 RF CONTROL
A link repeater listens to the link transmitter with a receiver on the link transmitter frequency and rebroadcasts the audio (repeats the audio) on another frequency. All base stations within acceptable signal strength range of the link repeater require a link receiver to be installed in the station on the link repeater transmit frequency. Key control for the link repeater is accomplished with HLGT and activity similar to the link transmitter. A second link repeater could be added in a daisy chain fashion to extend system coverage again. Each successive link repeater requires an additional transmit frequency to avoid unwanted RF collision of information. All base stations within acceptable signal strength range of the second link repeater require a link receiver to be installed in the station on the second link repeater transmit frequency. See figure 5 below which graphically represents the link transmitter and link repeater system.
FIGURE 5. RF Link Transmitter and Link Repeater System Configuration
With this daisy chain link transmitter and link repeater configuration special system considerations must be made depending on the desired paging mode supported by the system. For a binary only system audio propagation delay is the crucial parameter for simulcast integrity. In this type of system the delay line settings for stations can be calculated by air mile distances from the link transmitters and repeaters. Stations which listen to link transmitter must be compensated by an additional 290 microseconds since each link repeater adds that much propagation delay to the stations it feeds relative to the originating audio signal. For a mixed system of analog and binary paging, an audio equalizer may be needed for the second link repeater to properly phase the audio for analog simulcast. This is dependent on the users level of desired quality of the signal in the overlap area of the first and second link repeater.
Motorola offers link transmitters and repeaters in Midband, VHF, UHF and 900 Mhz. bands. Link transmitters are also available in a hot standby configuration. This is recommended for RF control systems since the channel must be up at all times for paging service to be provided. Battery back-up configurations are also recommended if AC power failures are of concern at the site. Battery back-up operation provides limited service to counter AC power losses of several hours. To guard against co-channel users and intermodulation in high RF environments, Motorola link transmitters and repeaters can be operated with Private Line (PL) or Digital Private Line (DPL) signaling. PL and DPL are forms of coded squelch used by the receiver as a qualifier for un-squelching. This effectively adds password type security to receiver access as opposed to just RF carrier un-squelching a receiver.
As mentioned earlier link transmitters and link repeaters are keyed using HLGT. HLGT duration should be kept at a minimum to avoid wasting system air time, however it must be long enough to guarantee reliable system keying. The duration of HLGT required for the system is determined as follows. Each link transmitter and carrier squelch link repeater require 120 milliseconds of HLGT to key. Each link repeater with DPL squelch requires 300 milliseconds of HLGT to key. If the paging transmitters use DPL squelch receivers then add an additional 180 milliseconds of HLGT. System required HLGT duration equals the sum of HLGT for the link transmitter, plus any carrier squelch link repeaters, plus any DPL squelch link repeaters, plus 180 milliseconds if the paging transmitters have DPL link receivers.
3.1 WIRELINE DISTRIBUTION CHANNEL
3.2 SATELLITE DISTRIBUTION CHANNEL
Satellite transmissions are hampered by "sun outages" and rainfall. Sun outages predominantly occur around the Spring and Fall equinox for several week periods. The outages can typically last anywhere from 0 to 10 minutes or less and can be predicted. The phenomena occurs when the sun lines up with a geostationary satellite in a direct path with the receiving antenna dish. The signal is swamped out by receiver noise when this occurs and reliability is greatly reduced. Due to the predictability of the phenomena the paging operator can inhibit paging however customer service is greatly hampered. Rainfall, which can occur at anytime, also degrades satellite reception. The effect of rainfall degradation can be countered by increasing the satellite receiver signal strength with an increase in dish size. As can be expected and increase in dish size also implies an increase in cost.
Satellite service currently provided for use in paging transmitters is in the C-Band (4-6 GHz.) and Ku-Band (12-14 Ghz.). Both bands have their respective advantages and disadvantages. C-Band is less vulnerable to rainfall effect and up link service fees are less than Ku-Band, however terrestrial microwave interference is a greater risk and receiver equipment is costlier compared to Ku-Band.
Ku-Band receive equipment is less susceptible to terrestrial microwave interference and less expensive compared to C-Band. Ku-Band however is effected more by rainfall and up link service is costlier compared to C-Band. Satellite service providers offer a variety of modulation methods and service in both the analog and digital transmission modes. The current available analog transmission technologies are FM squared, Single Side Band Suppressed Carrier (SSBSC), and Single Channel Per Carrier (SCPC). The current available digital transmission technologies are FM squared, FM cubed, and Single Channel Per Carrier (SCPC). The proper technology is selected based on a variety of system factors including, level of desired reliability, geographic service area, paging formats supported by system, analog or digital transmission requirements, cost,equipment availability and multiple vendor sourcing, etc. . . Consult systems engineering for further information.
Motorola offers several stand alone controllers for interface with a paging terminal for TRC and DRC control. The paging TRC protocol has been licensed to several large terminal manufacturers therefore a TRC controller is not needed in systems where the terminal can perform TRC encoding. For DRC systems the protocol is propriety and a controller is always needed.
4.0 PAGING STATION CONTROLLER (PSC)
4.1 SIMULCAST SYSTEM CONTROLLER
4.2 DIGITAL DIAGNOSTIC CONTROLLER
The DDC DRC system supports link transmitter and repeater keying and up to four frequency paging transmitter keying on up to 256 sectors for analog and binary paging. The DDC can service 1024 individual DRC transmitters for testing purposes and individually key any group of up to four transmitters. The DDC uses DRC1 MDC 1200 messaging for communicating information to and from the transmitters. Diagnostic messaging requires an audio feedback path from the base stations to the controller. This feed back path can be either an RF return path or wire line return path. The RF return path requires a monitor receiver on the paging transmitter frequency to allow for base station generated messages to be recovered by the DDC. For systems requiring more than one receiver a SpectraTac Voting receiver configuration is required. This system mode of operation is often referred to as "Over the Air" diagnostics and messaging. If dedicated wire lines are available from each transmitter site then diagnostic messaging can be accomplished using an audio combiner to return the DRC audio to the DDC. The system operator chooses which feedback path is more appropriate for their system. The feedback path has no bearing on paging throughput. Diagnostic messaging is a background operation to be performed when no paging requests are present. Paging has priority and diagnostics will be interspersed with paging traffic when diagnostics are invoked. If the system is heavily loaded diagnostics may take hours to complete.
The DDC has one standard hardware model, N1450, and can be upgraded in software for added communications features and capabilities. The standard DDC comes with a 120VAC power supply, a Video Display Terminal, a 50 pin punch block and all required interconnecting cables. The unit can be rack mounted or left stand alone. Additional options are available including 230V AC power supply, Omit VDT, -48V DC power supply, and extended cable lengths (25 and 50 ft.) for long VDT and punch block runs. Peripheral equipment such as a printer and modems for remoting the VDT are also available. Motorola publication 68P81000B80, Digital Diagnostic Controller N1450 Users Guide and Installation Manual, should be consulted for further detailed information regarding operation and capabilities. Motorola publication 6881000B85, Digital Diagnostic Controller N1450, should be consulted for hardware servicing information.
4.3 ENHANCED DIGITAL DIAGNOSTIC CONTROLLER
Enhanced DDC New Features
Database Back-up: Two DDC's can be connected via a straight dB 25 cable using serial port 3 on the back of each unit. Configuration plug DTE3 on one of the units must be made opposite of the other. Once this is done then the contents of the memory from one DDC can be transferred to another unit or it can be retrieved from the other unit. This allows the system operator to configure a second standby DDC automatically, avoiding tedious key stroking and complete database reprogramming in the second unit. The feature can also be used to keep the standby unit current when changes are made to the main DCC database. This is a manually invoked process, therefore the standby unit will not automatically update when connected to a DDC whose database is modified.
Automatic Diagnostic Polling Changes: Diagnostic polling was intended to run as a background task so as not to interfere with paging throughput. On heavily loaded systems a situation can develop where diagnostics are unable to squeeze in between paging traffic to complete a full system poll. To combat this the user can force the polling cycle by giving it priority over paging. The terminal will not be granted a Clear to Page until polling is completed. The terminal must have sufficient batching capability, several minutes, so that it does not run out of memory and lose pages or crash when inhibited. The standard DDC can be programmed for automatic diagnostic polling on the hour and only 5 times during the day. The enhanced DDC firmware still supports 5 programming times however a mode can be selected whereby diagnostic polling is performed every single hour, 24 times a day. The enhanced firmware also supports a TTL input signal, EXTERNAL POLLING TRIGGER, to let the user invoke a full system diagnostic poll at any time, and provides an external TTL POLLING IN PROGRESS output signal. This feature is activated by hardware jumper, JU17 (B position). This feature, when used, will replace the standard punch block signals ABORT (becomes EXTERNAL POLLING TRIGGER) and CHANNEL LOCKOUT (becomes POLLING IN PROGRESS).
HLGT duration was increased and unnecessary transmissions of HLGT were eliminated: HLGT is used to key up link transmitters and repeaters in an RF link distribution system. The standard DDC provided a jumperable maximum HLGT duration of 900 milliseconds. It was found that some large RF link systems with multiple hops required HLGT durations in excess of 900 milliseconds. The enhanced software in conjunction with a hardware jumper change extended the maximum HLGT duration to 3.3 seconds. The standard DDC firmware also resent HLGT between DRC messages when it really wasn't necessary. To increase efficiency HLGT is now stripped from back to back DRC messages since the audio activity keeps the link keyed and the controller need not resend HLGT if the link is keyed. These changes to HLGT operation were also made to the standard DDC firmware,version 1.5F or greater.
DDC control of paging transmitter simulcast parameters, alarms and wildcard outputs: The enhanced DDC firmware can remotely read and write the digital delay line setting (0-2555 microseconds in 5 microsecond steps), the station analog audio gain (-6.4 to +6.2 dB in .2 dB steps), the audio inversion status, the carrier frequency offset, the forward and reflected alarm threshold settings, and the status of the four external wildcards. For full utilization of this feature, the base stations must be equipped with digital delay lines, digital wattmeters, remote frequency adjust hardware, wildcards, and enhanced base station software to decode and encode these additional DRC 1 MDC 1200 messages. Functionality of this feature will be determined by the amount of base station options present. This feature is a convenience type feature which allows the system operator to make programming changes without the need for a site visit. This feature also aids in simulcast optimization since the system operator can vary individual station simulcast settings while field personnel observe the performance of the system in the critical overlap areas.
4.4 ADVANCED SIMULCAST CONTROLLER 1000 (ASC 1000)
For DDC replacement applications the following two points should be noted. The ASC punch block is not pin for pin compatible with the DDC 50 pin punch block for signal pin outs. The user will be required to punch down a new punch block for proper signal connection to the ASC from the existing system. When an ASC is used to replace a DDC a new punch block must be wired into the existing system. There is one feature that the ASC 1000 does not support that is available with the Enhanced DDC. The feature is an external diagnostic polling trigger (DDC ABORT signal) and a polling in progress handshake (DDC CHANNEL LOCKOUT signal). See the Enhanced DDC section "Automatic Diagnostic Polling Changes" for more detailed feature explanation.
The ASC 1000 also brings new features and capabilities not available with the standard or enhanced DDC. The ASC 1000 supports the following new features:
4.5 ADVANCED SIMULCAST CONTROLLER 1500 (ASC 1500)
The ASC 1500 is intended for use in systems which desire to fully utilize all the capabilities of the Advanced Control base station. Unlike the ASC 1000 which communicates using DRC 1 messaging only, the ASC 1500 communicates using DRC 2 messaging exclusively. DRC 2 messaging was invented to allow for additional messaging and communication as well as future expansion between the Advanced Control Base station and the ASC 1500. Due to the exclusive DRC 2 messaging used by the ASC 1500 it is required that the base station infrastructure be of the Advanced Control type. The ASC 1500 provides basic paging system operation with the following additional capabilities. Usage of some of the addition system features may require additional peripheral hardware such as modems,printers, etc.
Unsolicited Alarm Reporting: The ASC will report alarm information sent by an Advanced Control base station even though the ASC was not requesting alarm information from the station. Alarm information is forwarded to the ASC by dedicated return wire lines or dial-up phone lines. This is a real time alarm reporting method. Dedicated wire lines provide the fastest message response time. In a dedicated return wire line system message collisions between competing stations can occur. To counter the effects of data collisions the base station randomly keeps sending the alarm message until the ASC acknowledges the base station with a receipt confirmation. The ASC acknowledges the base station via the outbound control channel. Paging is temporarily inhibited while the ASC acknowledges the station. For a wire line return path, a phone line audio combiner is required to sum all the station wire lines to one input audio port on the ASC. For a dial-up phone line return path system a modem and dial-up phone line is required at each base station and one at the ASC. A Dial-up phone line return path system will add a small delay due to modem dialing and connect time when reporting an alarm. Alarm message collisions from multiple stations are not an issue since the phone system will busy out stations when the ASC is currently servicing an alarm from another station. Busied out stations continue to retry until a connection with the ASC is established. When a station gets through to the ASC it is acknowledged immediately via the modem connection so no inhibit of the paging system is required. An occasional full system diagnostic poll via modems would be required to determine if any of the dial-up phone lines are inoperative or a station is completely dead.
Dial In Dial Out Diagnostics: Traditional diagnostic polling requires the paging channel to be inhibited while diagnostic messaging is in progress. This can become a problem for heavily loaded systems which are at maximum user capacity, throughput is already poor and the channel is continuously in use not allowing diagnostics to ever complete. Dial In Dial Out Diagnostics is a method for allowing diagnostic polling without interrupting paging service. The feature requires the ASC to be equipped with a modem and dial-up phone line as well as each station having a modem and dial-up phone line. When polling is initiated by the ASC it will attempt to dial each station and interrogate the station for any alarms. The process runs in parallel with paging activity and does not inhibit use of the paging channel.
Automatic Delay Equalization: This feature allows the ASC to automatically measure relative individual base station audio propagation delays for the outbound control path which feeds each station. Once all the data is acquired and evaluated, the ASC will automatically compensate individual station digital delay lines such the system is operating optimally for simulcast binary paging. For the feature to be operational, the system must have a SpectraTac monitor receiver infrastructure in place and all transmitters must be able to communicate back with the ASC through the SpectraTac system. The base stations must all be of the Advanced Control type. For binary paging, audio delay compensation is the parameter of importance for simulcast integrity. This feature will not compensate for critical analog voice paging parameters such as audio gain, and transmitter carrier frequency drift. This feature is an automatic equalization system for binary paging only. Analog paging supported on the system will still have to be attended to via manual testing and compensated for manually. From the ASC, the station audio gain and carrier frequency can be adjusted by editing and writing the station parameter settings for audio gain and carrier frequency. (See the Auto Equalization document, not yet published, for detailed system requirements, installation and alignment information)
Remote Logging Printer: The ASC supports logging system and station alarm information to a remote printer. This allows the user the capability to monitor system activity from several operations across the country from a central location. The feature requires two external modems, one at the ASC and one at the printer location, a dial-up phone line, and a printer. The ASC will dial out and connect to the printer when ever new system or station alarm information is received and provide a time stamped hard copy of the alarms. The ASC error log information is maintained locally internal to the ASC database for local inspection as well.
Direct Digital Interface: For RF link and wire line control information distribution systems, the ASC output is in an analog format composed of DRC MDC modem tones, FSK paging modem tones, signaling tones, and voice. For a digital satellite channel analog information cannot be transmitted and the information to be transmitted must be in the digital format. For this type of specialized system, binary only paging can be supported since tone and voice transmissions cannot pass through the digital satellite channel. The DRC MDC modem tones and FSK paging modem tones originate as digital information in the ASC and are converted to analog signals for transmission in RF link and wire line systems. For the digital satellite distribution channel the ASC base band digital information is fed directly to a satellite up link and transmitted to each base station. The base station receives the digital bit stream from a satellite receiver and processes control and paging information accordingly. Diagnostics for this type of system are still possible but require an analog return path, return wire lines or a SpectraTac monitor receiver voting comparator system, from the transmitter network. Diagnostic messages are sent to the transmitters in the digital format and base stations responses are received by the ASC in the analog format.
N+1 Redundancy: As mentioned earlier an ASC 1500 is comprised of a power supply card, a memory card, and an Advanced Transmitter Control card, ATC for short. One ATC card is required to control a single channel of transmitters. The ASC card cage can support up to five ATC cards, therefore 5 separate channels can be controlled from a single ASC card cage when five ATC cards are present. N+1 redundancy refers to a special wire line control system configuration whereby up to 4 channels, all in the same frequency band of operation, VHF, UHF, or 900 Mhz, can be backed up by one transmitter as a hot standby in the event a transmitter failure occurs on one of the channels. This type of system implies that each transmitter site has one transmitter from each channel present. In addition each of the site transmitters is connected to a Motorola designed N+1 redundancy panel which contains wire line and antenna switching circuitry controlled by the standby transmitter. The standby transmitter can then fill in for a transmitter on a channel that it recognizes has a problem. The standby transmitter, also referred to as the master station, communicates with all the other stations, referred to as slaves, via a station Local Area Network, LAN for short. The master station continuously polls all the slave transmitters via the LAN to determine if a problem exists, and switches in for a station when a failure is detected. N+1 redundancy therefore refers to the ASC 1500's ability to manage and maintain such a complex system of up to four channels with a single backup transmitter. The feature is primarily used in international markets where governmental agencies are the primary paging service providers. These types of systems have not yet been introduced into domestic U.S. markets.
Forward Power Readings Saved in Ram: The ASC 1500, which uses DRC 2 messaging, has the capability to acquire station forward and reflected power readings during diagnostic polling in addition to station alarm information. The DRC 1 format had limited messaging capabilities, hence the creation of the DRC 2 format to allow for such improvements in station communications. The ASC will save a history file for each individual transmitter that is polled. The file contains the status of the station power readings and alarm information for the last three diagnostic polls performed. The history file will overwrite the oldest logged entry with a new entry as polling continues.
5.0 MICOR PURC
Antenna connections to the link transmitters are of the UHF female type for all links except the 125 Watt Midband link. The 125 watt Midband Link is a hybrid station comprised of Micor control and low level RF circuitry with PURC 5000 power supplies and PA decks. The link transmitters are offered in a hot standby redundancy configuration in the event a failure occurs in the main station. Without a back-up unit a failure to the link transmitter would render the system useless until the link is repaired. It is strongly advised that systems be engineered employing hot standby configurations for link transmitters. Link transmitters are also available with battery back-up/charging operation in the event an AC power outage occurs at the site. The stations are also available with alternate AC power supplies for use in international markets. For servicing it is advised the links be ordered with a wattmeter and power and modulation alarm indication.
5.1 PURC 5000
6.0 MICOR LINK REPEATERS
6.1 PURC 5000 LINK REPEATERS
The link repeater is a link transmitter with a link receiver added to it. Link repeaters are not restricted to a particular frequency band for operation, the transmit and receive frequencies can be from different bands. Midband, UHF, or 928-960 Mhz. link receivers can be used to make a link repeater. For link receivers in the 928-960 Mhz. band both 25 Khz or 12.5 Khz channel spaced receivers are available. The Link Repeater has a flat audio response and keying is accomplished using HLGT. Once keyed, the link repeater will remain keyed until audio activity has ceased. Upon loss of activity the repeaters will drop off the air. The drop out delay is adjustable and user set to 2, 4, or 8 seconds. The repeaters are capable of generating Digital Private Line signaling to reduce problems due to co-channel users in the same geographic area. Link repeaters are offered in a hot standby redundancy configuration in the event a failure occurs in the main repeater. Without a back-up unit a failure to the link repeater would render the stations which listen to the link repeater useless until the repeater is repaired. It is strongly advised that systems be engineered employing hot standby configurations for link repeaters. Link repeaters are also available with battery back-up/charging operation in the event an AC power outage occurs at the site. The stations are also available with alternate AC power supplies for use in international markets. For servicing it is advised the link repeaters be ordered with a digital wattmeter.
PAGING BASE STATIONS
7.0 MICOR TRC
The low power transmitters are fully solid state. The high power transmitters are fully solid state except for the power amplifiers which still use a tubes for the finals. Transmit and receive frequencies are crystal controlled and not synthesized across the band of interest. Transmit and receive frequency changes require channel element changes and retuning. The stations are available in both wire line and link receiver control.
The Micor family of paging transmitters are available in both indoor and outdoor cabinets and require both rear and front door access for installation and servicing. The internal component assemblies typically have a gray or silver finish. The stations are typically referred to as one of two type, either UNIFIED or NON-UNIFIED, describing the control chassis mechanics. The unified control chassis houses control, receiver and transmit exciter circuitry. The non-unified control chassis houses only the control circuitry, the receiver and transmitter exciter are separate components. The control chassis is a modular design with various control cards which are interconnected by a connectorized back plane. Two separate back planes exist, one for the unified chassis and one for the non-unified chassis. All connections to the back plane are made by either screw terminal, bubble pins or specialized connectors. The control cards are the same for both unified and non-unified stations. The stations are fully factory assembled and tested for analog and binary operation. The delay line option if ordered is a drop ship item and installed in the field on installation. The delay line is an passive delay line manufactured by Allen Avionics and ranges in delay from 0-1100 microseconds, adjustable in 5 microsecond steps. The paging modem is also a drop shipped item which is installed in the field during station installation. The modem converts incoming FSK audio paging tones into RS-232 level digital signals which are then used to modulate the transmitter as FSK-NRZ data.
The paging modem used is a Bell 202 type modem which uses 1200 & 2200 Hz. modem tones. The recommended modem is manufactured by Universal Data Systems, a Motorola owned subsidiary. The original manufactured modem has since been redesigned to new model which can only be identified by a size comparison. The new modem is smaller in size as compared to the original old modem. In addition to being smaller in size the new modem is much faster in passing data as compared to the old modem. In the event an old modem is replaced it with one of the new small modems it will have to be slowed down by using a QRN4612 modem delay module. This is required for simulcast compatibility.
Micor stations are available in both simulcast and non-simulcast models. For non simulcast models the paging synthesizer and delay lines will not be required. The stations are designed for receiver flat audio, the transmit audio can be either flat or pre-emphasized. Early analog paging systems used pre-emphasis in the stations for voice paging, however this function was moved to the paging terminal and the base station transmit audio path is predominantly ordered with flat transmit audio. For simulcast systems it is much better to pre-emphasize the audio once at the source than have all stations pre-emphasizing the audio independently.
The Micor PURC paging stations come standard with Paging Universal Remote Control (PURC), a Tone Remote Control format for transmitter keying in the analog and binary mode. Depending on the type of station ordered, simulcast or non-simulcast, the paging synthesizers and delay lines will be optional. Power supplies and PA decks will vary depending on the frequency band, power out, and desired AC line voltage option. Figure 5 below illustrates the general structure of a Micor PURC paging station for a Unified and Non-Unified chassis.
FIGURE 6. Micor Unified and Non-Unified Transmitter Block Diagrams
7.1 MICOR DRC
The new integrated control chassis replaces several existing station components as well as adding new features never before possible with Micor stations. The control tray has a built in Bell 202T paging modem which comes standard with the tray. An optional digital wattmeter and delay line can be ordered for full station capabilities. The DRC option with digital delay line will replace the existing UDS 202T modem and passive Allen Avionics delay line. The digital delay line has over twice the range, 2555 microseconds versus 1100 microseconds, of the Allen Avionics delay line. The DRC option requires the station to have transmit flat audio for proper operation. Stations without transmit flat audio must be upgraded prior to installing the DRC option.
The Micor DRC option uses DRC 1 messaging. The new control option allows for positive control, increased sector paging, individual station testing, and station diagnostics for alarms and forward and reflected power readings (when equipped with a digital wattmeter). The option also is compatible with Motorola dial-up diagnostics which run off of an IBM PC or compatible when equipped with a Hayes 212 modem or equivalent. The station can be controlled by either a DDC or ASC 1000. The DRC option has a software upgrade allowing it to have the wattmeter delay line board parameters remotely controlled manually. The software upgrade works with an Enhanced DDC or an ASC1000. The Micor DRC option is available as a field retrofit kit for both Unified and Non-Unified stations or can be factory installed.
The DRC option is not compatible with monitor receiver, time out timer, and voice actuated response (VAR) as supported with Micor PURC stations. The option is compatible with Low Band, VHF, and UHF stations, both high and low power. The option is not compatible with 900 Mhz. Micor stations due to a mechanical incompatibility with the 900 Mhz PA deck and the control tray folding out for alignment. Electrically the DRC option will work in a 900 Mhz. Micor station however installation, alignment and servicing will be a bit inconvenient The product was never intended to operate with 900 Mhz. stations since PURC 5000 900 Mhz. stations are simulcast compatible with Micor and the Micor 900 Mhz station was intended to be canceled. Figure 6 below illustrates the option as installed in a Micor station.
FIGURE 7. Micor DRC as Installed in a Unified and Non-Unified Station
The Micor DRC option is made up of 4 primary PC boards, in addition to the two back plane boards, one for unified and one for non-unified stations. The DRC control module is actually made up of two boards, a Control Processor Board (CPB) which handles all the logic interface to the rest of the control tray, and a Modem board which processes incoming DRC audio as well as generating DRC audio for diagnostics. The Micor Paging Control Board (MPC) performs transmit audio processing and supervises overall control tray operation and interface with the station. The digital wattmeter and delay line board function is self explanatory.
7.2 MICOR ADVANCED CONTROL
The Advanced Control Option for Micor station is offered as a field retrofit kit only. The tray is interfaced to the Micor station using the Micor DRC back plane, Unified or Non-Unified, depending on the station type. The tray is mounted towards the bottom of the station. The space evacuated buy the UDS modem and Allen Avionics delay line is utilized to provide room for the Advanced Control Tray. The Paging synthesizer is relocated to the space where the modem and delay line were and the Advanced Control Tray is mounted in the location where the paging synthesizer originally was. See the Advanced Control Retrofit for Micor PURC Paging Stations manual, part number 6881127E15 for detailed application information.
FIGURE 8. Advanced Control Tray Hardware Block Diagram
The Advanced Control Tray is microprocessor controlled and uses Digital Signal Processing, DSP, for audio processing. The tray is a 19" rack mount stand alone tray. The control tray is made up of 4 printed circuit boards, the Advanced Control Board (ACB), the Power Supply Line Interface Board (PSLIB), the Display Board, and the Back plane board. The back plane board is fastened to the tray and the ACB and PSLIB board plug into the back plane. The back plane board provides connectorized interface for the tray modules as well as interface to the rest of the station hardware. The display board physically snaps into the front panel and plugs into the ACB board via a ribbon cable. The display board is made up of an 8 character alphanumeric display, 8 status and indicator LEDs, and a 16 function key pad for locally operating, programming, and aligning the station. The front panel flips open for servicing of the ACB and PSLIB board.
The ACB board performs control audio processing, synthesizer programming, transmit audio processing, and station and system level alarm recognition and reporting. The board contains no user adjustable potentiometers and board status, configuration, and alignment is accomplished via the display board display and keypad. The PSLIB board generates +5 volts for use by the logic circuits, from station supplied +13.8 and +9.6 volt supplies. Filtered +13.8 and +9.6 is passed through the PSLIB board to the ACB board for use by the audio processing circuits. The PSLIB board also contains phone line interface circuitry for wire line control stations. The tray is also available with an internal dial up/dial out modem with battery back-up and charging for diagnostic messaging. If ordered the modem is piggy backed on the PSLIB board. The batteries mount to the control tray cover above the PSLIB board. The tray comes with a wiring harness for interface to the rest of the station and the outside world.
7.3 PURC 5000 STATIONS
The PURC 5000 family of paging transmitters are available in both indoor and outdoor cabinets. The station hardware and cabinet design have been reduced in size compared to the Micor transmitters. Station installation and servicing only requires single side access from the front of the station. All antenna, power, and control connections are made at the side of the station via the station J-box. This type of design allows the stations to fit flush against a wall or mount back to back in congested sites. The stations can also be stacked one on top the other. The 300 watt 900 Mhz station is the only exception, due to the PA and power supply requirements. The 300 watt 900 Mhz. station comes in either an indoor or outdoor cabinet and requires both front and rear access. All internal component assemblies either slide out on rails or fold out for servicing. The internal component assemblies are painted with a black finish.
Non-Simulcast PURC 5000 stations come standard with, Tone Remote Control, wire line control, a built in Bell 202 paging modem, minimum size required indoor cabinet, 120 V 60 Hz. AC power supplies, cooling fans depending on the make and model, RF tray and control as shown minus the wattmeter/delay line, and one or two PA decks depending on the power out, and a Low Pass Filter. Simulcast PURC 5000 stations come standard with all the Non-Simulcast station feature in addition to adding a Paging Synthesizer for increased TX frequency stability. Additional ordered options include a link receiver for RF control, digital wattmeter option for power out monitoring, digital delay line for simulcast equalization, second expansion tray for special applications using wild cards or RS232 communications, double and triple circulators, international power supplies capabilities, battery back-up options for stations, alternate cabinets, outdoor models or dual access Micor type cabinets, and Digital Remote Control. See figure 9 below for a visual representation of the PURC 5000 station.
PURC 5000 STATION BLOCK DIAGRAM
FIGURE 9. PURC 5000 Paging Transmitter Block Diagram
7.4 PURC 5000 CONTROL TRAY
FIGURE 10. PURC 5000 Control Tray Hardware Block Diagram
The control board slot can be occupied by either a TRC board or a DRC board pair. These control boards are microprocessor based and process both logic and audio information . The control boards continuously monitor incoming audio to the tray for control messages. The control boards do not process transmit audio. They exclusively perform control audio demodulation and via the muxbus tell the Station Control and PURC board what mode of operation to be in. TRC control provides no station transmitted diagnostic information, but DRC control does. DRC control allows for diagnostic messaging over the air or via the station line 2 wire line. The control boards contain line 1 interface and line 2 driver circuitry for phone line interface. See figure 10 below for an exploded view of the control tray.
First Expansion Tray
The PURC board is a microprocessor based board responsible for processing analog and binary paging information. The PURC board monitors incoming station audio and will process analog voice or tone pages, or convert FSK modem tones to logic levels for binary paging. The PURC board controls the analog deviation, nominal and maximum, as well as providing binary deviation alignment for non-simulcast stations. The PURC board also has responsibility for supervising the wattmeter delay line board operation. The PURC board contains wattmeter look up tables for the various frequency bands. The look up tables are stored in program prom, therefore the code will vary from board to board, depending on the station frequency band and type of wattmeter element used in the station. The board firmware has several SP's available for the various bands to operate in a Key on Data mode for binary only systems. The board can also be jumpered to pass TTL or RS232 external paging data for applications where the internal paging modem is not needed.
The wattmeter delay line board is equipped with a three digit seven segment display to provide the user with visual information regarding station forward power output, reflected power and a calculated VSWR, when the station is equipped with a wattmeter element. The wattmeter option also allows the user to set alarm trip points when the forward power falls below the forward alarm set point or the reflected power rises above the reflected alarm set point. The display is also used to show numerically the station settings for the digital delay line. The digital delay line has a maximum delay of 2555 microseconds in 5 microsecond increments. The clock circuitry can be jumpered from 100 Khz. to 200 Khz. thereby changing the resolution to 10 microsecond steps and the total board delay is then doubled to 5110 microseconds. The change in clock rate degrades the delay line audio performance and should not be used for voice paging applications. The degradation can be tolerated by binary only paging systems running Golay or 512 POCSAG paging, usage with 1200 baud POCSAG is not recommended. The wattmeter digital delay line board contains audio gain and attenuation circuitry ranging from -6.4 dB to +6.2 dB in .2 dB steps. This board capability is only used for DRC stations equipped with remote gain and delay adjust.
Second Expansion Tray
For PURC 5000 stations there exists an IBM PC based program which will display the station muxbus and allow the user to read forward and reflected power from a station equipped with a digital wattmeter. The feature requires the station to have a second expansion tray which houses a wildcard module and an RS 232 interface module. The station must also be equipped with an external auto answer Hayes compatible modem that runs at 300 or 1200 baud and must be connected to a dial-up phone line. The PC must also be connected to a Hayes compatible modem that runs at 300 or 1200 baud and be connected to a dial-up phone line. With this hardware in place the user can dial up a station and monitor transmitter muxbus bus information in real time. The various keying modes can be deduced from the muxbus bit status. Power readings will be displayed numerically and a VSWR calculation will be made when power readings are requested.
7.5 PURC 5000 TRC
7.6 PURC 5000 DRC
For additional station communication features a software upgrade is available, commonly referred to as "Enhanced DRC" software which allows the user to modify the wattmeter delay line board settings remotely. The upgrade option is typically referred to as the "Remote Delay, Gain and Frequency Adjust" option. The software upgrade is made to the DRC CPB board and the PURC Board. New proms are required as well as adding an EEPROM to the PURC board so wattmeter delay line board settings are preserved in non-volatile memory. The upgrade also requires the DDC controller to be upgraded to Enhanced DRC operation with a software version of 2.X. (the X merely indicates the latest release and any upgrades). The software upgrade can be factory installed or upgraded in the field with the appropriate retrofit kit. The field retrofit kits are frequency sensitive since the PURC board contains wattmeter look-up tables which are not the same for all frequency bands and elements used in production. The Enhanced DRC software package allows the user to read and modify the station delay line setting, change the power alarm trip point thresholds, control station audio gain from -6.2 dB to +6.4 dB, and tweak transmit carrier frequency from 30 to 200 Hz depending on the frequency band of the station. The remote frequency adjust capability requires the station to have a paging synthesizer which has been modified to support this feature. In addition the user can remotely control 4 output wildcard bits for controlling third party site equipment.
7.7 PURC 5000 ADVANCED CONTROL
The tray is made up of 4 standard PC boards and an optional dial-up dial-out modem with battery backup for dial-up diagnostic capabilities. The ACB board is the main control board responsible for interface and control of the rest of the station. The ACB board contains all the audio and binary processing circuitry. The PSLIB board is a Power Supply Line Interface Board with generates local +5V for the tray logic circuitry. In addition the PSLIB provides interface for telephone line connects for incoming and outbound audio. The PSLIB board also supports the internal station dial-up dial-out diagnostic modem (optional) with battery backup (optional).
Both the ACB and PSLIB boards plug into a back plane board for easy field replacement. The back plane is screwed down to the metal tray enclosure and requires no service accesses. All interface cable connections are conveniently made from the front of the back plane board. The tray is sloped down towards the back allowing easy access to interface connectors. The Advanced Control Tray comes with an interface cable harness specially designed to minimize cable clutter. The Advanced Control Tray design no longer requires the tray to slide out on rails thereby reducing the risk of pinched cables as with the PURC 5000 control hardware in figure 10. As mentioned before all tray programming and station local access is accomplished via the Display board which has an 8 segment alphanumeric readout. Led indicators for critical station operating status indication, and a 16 function key pad for menu access and data entry. See figure 11 below for Advanced Control tray pictorial representation.
FIGURE 11. Advanced Control Tray Hardware Block Diagram
Advanced Control in PURC 5000 stations is only compatible with Simulcast stations. The tray does not support local alignment of binary deviation for Non-Simulcast stations as the PURC 5000 control hardware of figure 10 does. All binary deviation alignment is performed in the paging synthesizer tray for Advanced Control applications. The paging business has progressed primarily to simulcast systems and the required design effort to support Non-Simulcast stations was deemed impractical. Customers desiring Non-simulcast transmitters with Advanced Control will have no choice but to PURChase a Simulcast transmitter at the additional cost of the paging synthesizer hardware.
The Advanced Control Tray is currently offered with DRC control only, TRC control is currently under development. The tray supports both DRC 1 and DRC 2 messaging standard unlike the PURC 5000 standard DRC which only supports DRC 1 messaging. The tray also includes standard digital wattmeter hardware, digital delay line hardware, RS 232 interface hardware, and wild card input and output hardware. The digital wattmeter and delay line options are still paid for options. The wattmeter option will source the station a wattmeter element and the delay line option will cause the factory to enable the delay line hardware in software. Even though DRC is the only control format currently supported by Advanced Control it too is a customer paid for option. When TRC development is completed it will be the standard shipping control unless the DRC option is ordered. Consult the Advanced Control users manual, part number 6881084E80, for complete detailed tray operation. Consult SMR-5861 for hardware schematics and troubleshooting information.
FEEDBACK PATH FOR INFORMATION FROM BASE STATIONS TO CONTROLLER
8.1 RF RETURN PATH
8.2 SPECTRATAC MONITOR RECEIVER VOTING COMPARATOR SYSTEM
FIGURE 12. SpectraTac Total Area Coverage System with Voting Comparator and Monitor Receivers
The SpectraTac Voting Comparator can support up to eight receivers per card cage. Up to three Voting Comparators can be connected together to allow up to 24 receivers to be supported in a voting configuration. The SpectraTac system also provides a return phone line check for continuity. When the receiver is squelched it sends a continuous tone of 2175 Hz., referred to as status tone, down the phone line. The voting comparator detects the presence of this tone and any loss of this tone without audio activity implies a break in the return phone line. The user is visually made aware of the failure by a led indicator.
8.3 SPECTRATAC MONITOR RECEIVER
FIGURE 13. SpectraTac Monitor Receiver Block Diagram
8.4 SPECTRA TAC VOTING COMPARATOR
FIGURE 14. SpectraTac Voting Comparator Block Diagram
The Voting Comparator can support up to eight monitor receivers. Each receiver phone line is connected a Squelch Quality Module (SQM) which checks for status tone and performs the audio quality check when a voting situation occurs. The SQM provides led display for status tone fail, module voted, and un-squelch indicate. The module can be locally disabled or monitored. The Command Module (CMD) routes the voted SQM module audio to a 600 ohm line driver. The Voting Comparator command module audio can drive a phone line or connect directly to the controller if co-located. Typically the voting comparator is co-located with the controller. Up to three voting comparators can be connected to allow for up to 24 receivers to be supported for voting on a single system. The Key module is used to key a DC or TRC transmitter for re-broadcasting comparator voted audio. This capability is not commonly used in the paging system however there is no restriction on using it. As mentioned earlier most voting comparators are co-located with the controller and do not require a RF hop to the controller site. For further detailed Voting Comparator information see Motorola publication 6881039E50, SPECTRA TAC Total Area Coverage Comparator.
8.5 SPECTRA TAC USAGE FOR AUTO EQUALIZATION WITH THE ASC 1500
The Squelch Quality Module was originally released as a TLN1718B kit and since then has been replaced with a TLN1718C kit. The C version module redesign included changes to the inhibit module logic circuitry which inadvertently created problems for use with auto equalization. C version modules are acceptable for standard voting applications however they cannot be used with the ASC 1500 for automatic delay equalization since the ASC cannot control the C version inhibit function. As a short term alternative the original module was brought back into production under an new kit number, TRN6091B. The TRN1718B SQM module or the TRN6091B module must be used for systems using an ASC 1500 and running automatic delay equalization.
8.6 WIRELINE RETURN
The dedicated wire line return path can also be used for Unsolicited Alarm Reporting when an ASC 1500 and Advanced Control base stations make-up the system. Stations capable of unsolicited alarm reporting will send MDC messages to the controller when an alarm condition is detected. Since all the return wire lines are combined together, it is possible for two or more stations to be sending information and have the data corrupted by a data collision. To alleviate the problem of data collisions, the stations will continue sending alarm messages in a random fashion until the controller services the alarm with an acknowledge to the station. This acknowledge requires the control channel to be inhibited from paging while the ASC 1500 services the station.
8.7 MODEM CONNECT VIA THE PUBLIC SWITCHED TELEPHONE NETWORK
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