Telemetry system for automated remote calling and central dispatch of services, particularly taxicabs
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention concerns telemetry systems permitting remote registration of requests for services at a central dispatch point of such services, particularly permitting registration by radio of digitalized service requests at a computerized central dispatch point for taxicab services. 
     2. Background of the Invention 
     It is known in the prior art to transmit encoded signals from a multiplicity of remote, transmitting, locations to a central, receiving, location. Such prior art systems are often for transmitting alarms, and for summoning emergency services. Such prior art systems may transfer messages unidirectionally or bidirectionally, including by radio. However, they generally differ from the system of the present invention, amongst other aspects, by failing to transmit message information in digitalized form, by failing to accord for conflicts between multiple messages simultaneously transmitted upon a single communications channel, and by interpreting and processing all messages manually as opposed to interpreting and processing messages by automated, computerized, means. 
     As an example of the prior art, U.S. Pat. No. 2,022,991 for an ALARM TRANSMITTING SYSTEM discloses an early use of radio in an alarm system. Switches concealed about the protected premises, or even concealed upon the person of an employee, are connected by wires, usually telephone lines, to a central alarm office. Upon the receipt of an alarm resultant from a switch closure at the central alarm office, an associated one telegraph phone reproducing unit is activated so as to broadcast predetermined instructions over a radio transmitter. These predetermined instructions direct a particular police car, assigned to the neighborhood from which the alarm has been received, to proceed to the premises or person upon which the alarm system has been activated. An early attempt showing the use of radio, and an attempt to discriminate between the message and the response thereto, is shown. 
     U.S. Pat. No. 2,989,621 for FIRE ALARM SYSTEM USING A PLURAL OSCILLATOR RADIO TRANSMITTER to P. M. Barton, et al., shows a fire alarm system using radio rather than wired communication for transmitting alarms from a multiplicity of alarm boxes to a central receiving center. The signals broadcast by the different transmitters within the same alarm system are modulated with different audio tones so that the particular alarm box from which each signal has been sent may be identified. The possibility that more than one alarm may be simultaneously active is encompassed by providing that the number of alarm boxes within each alarm unit system shall be limited to the maximum number of separately and identifiable audio tones, or tone combinations, that can be transmitted within a radio frequency channel. At the preferred operational frequency of 2250 to 2700 kilocycles per second, preferred radio channel band width of 10 kilocycles, and preferred modulation frequency of 400 to 4000 cycles in 100 cycles per second increments, some 37 different audio tones, or 37 alarm boxes, are available per unit system. This modest number, already emplacing a very demanding requirement upon the human ear which must discriminate all combinations of the multiple signals, is evidence of prior art problems with analog (audio frequency) modulation of radio alarm signals, and with the possible interference between such signals. 
     U.S. Pat. No. 3,256,517 for a REMOTE ALARM SYSTEM WITH SCANNING BY TONES to T. Saltzbert, et al., shows the use of a single transmission channel for a plurality of alarms on a time-shared basis. Particularly, communication via radio link between the remote alarm points and the central stations is bidirectional. The central station transmits interrogations to the remote locations in sequence by use of an addressing code, typically three tones of different frequencies. Each terminal equipment at the remote location responds only to its unique address, and transmits alarm information if and when interrogated. A bidirectional communication system of this nature increases cost. It incurs some latency between the time that an alarm may actually be sensed at a remote station and the later time at which the central station may interrogate the remote station to receive notification of the alarm. 
     U.S. Pat. No. 3,440,635 for POLICE ALARM to H. B. Hull discloses the use of portable radio transmitters which send coded signals that are received centrally by receivers equipped with direction finding capability. The direction finding equipment is sensitive to transmission of a signal at a particular frequency allocated for this purpose. The allocated carrier frequency may further be modulated with a tone of a particular frequency i.e., it may be encoded, in order to determine the location of the transmitter with increased accuracy. It is contemplated that the number of alarm transmitters, and users, will be small. 
     U.S. Pat. No. 4,630,035 for ALARM SYSTEM HAVING ALARM TRANSMITTER IDENTIFICATION CODES AND ACOUSTIC RANGING to Stahl, et al., describes an alarm system having a plurality of alarm units each transmitting an identification code. In some systems the alarm transmitters transmit the identification codes to a central control indirectly through one or more transponders. The transponders can also be assigned an address code, and can relay both the alarm transmitter identification code and their own address code to the central control when an alarm condition exists. The alarm units can generate, and the transponders can receive, an audio, as well as a radio, signal in order to aid in positional location of the alarm unit upon the occasion of an alarm. 
     Prior art telecommunications and telemetry systems for the automated transmission of alarms do not generally address the problem of multiple simultaneous transmissions. This is acceptable because the occurrence of alarms is normally very infrequent. Additionally, the emergency resource which may be provided in response to one or more alarms is usually limited, and it is of little consequence that later, successive, alarms should fail to be recognized if there is no remaining emergency resource to be dispensed in response to such alarms. 
     A contrary situation exists in a telecommunications, or telemetry, system for the registration of service requests, such as request for transportation services, particularly taxicabs. The number of service requests both per unit time, and at certain peak periods, would be expected to be very large. A number of service requests would normally be expected to be simultaneously, or nearly simultaneously, registered at distributed call boxes each of which is capable of initiating a service request. Finally, a large number of discrete resources, such as taxicabs, are normally available to be applied to the plurality of concurrent service requests. It is therefore useful that no service request should fail to be recognized even though a large system, entertaining many service requests from many distributed call boxes, should use but a single, narrow bandwidth, radio communications channel. 
     The present invention offers a solution to the telecommunications system problem for reliable registration, communication, and response to multiple asynchronous service requests (particularly transportation service requests, particularly requests for taxicabs). A prior art approach remotely analogous to the solution of the present invention is represented by wired communication channels within and between computers. Particularly, the well-known Ethernet communications channel employing microwave frequency digital communication between discrete points on a coaxial cable accords that a number of interconnected points may each asynchronously attempt to communicate with one or more additional points. In the event that two communications are simultaneously, or nearly simultaneously, initiated, then the receivers at all communicating locations are capable of detecting a collision situation on the communication channel, or coaxial cable. This detection of a collision, or conflict, condition, is based on energy levels. The detection is performed by the transmitting, as well as the receiving, units. In the event of any detection of a conflict, then both transmitting units will cease their attempted communications, and will wait a variable interval of time before asynchronously reinitiating such communications. Since the communications periods typically occupy but a small percentage of the total elapsed time, the stagger-staged communication between transmitting units usually accords that all messages will ultimately flow without conflict on the single communications channel. 
     It is inappropriate to adapt energy level sensing in order to detect communication conflicts, such as energy level sensing is performed upon an Ethernet communication net, to free space, radio, communication. Particularly, the strength of a radio signal, or signals, may vary in accordance with transmitters&#39; separation(s), transmitters&#39; power(s), and atmospheric conditions. It is unreliable to attempt to determine whether two or more radio transmitters are simultaneously active solely by the sensing of the radio frequency power density. 
     Alternatively, a full handshake communication system wherein the receipt of all messages is positively acknowledged is also inappropriate. Such a system is more costly resultantly from the use of bidirectional, as opposed to unidirectional, communication links. 
     The present invention will be seen to permit reliable, fully automated, communication of many independently originated, and asynchronously timed, messages upon a single radio communication channel without incurring either (i) the loss of messages or (ii) a large hardware overhead to ensure message receipt. 
     SUMMARY OF THE INVENTION 
     The present invention is embodied in a telemetry system for the remote registration of requests for services at, and to, a central dispatch point for such services. The invention is also embodied in a method of using such a telemetry system. 
     In accordance with one aspect of the present invention, the communication, and the communications&#39; processing, within the telemetry system is entirely digital. A plurality of call boxes each asynchronously transmits an individually unique digital code as services are requested. A central station receives the digital codes which are at times generated from the call boxes, and digitally processes the codes so as to produce a display intelligible to a human. The human dispatches a particular requested service to a particular requesting call box location. In accordance with the present invention, the transmitting and the receiving of the digital codes is preferably by radio, the processing of such digital codes is preferably by a digital computer, and the display of messages is preferably on a computer monitor and/or printer. The radio communication of digital identification codes is preferably by Frequency Shift Keying (FSK), preferably by a Bi-Phase Modulated (Bi-Phase-M) digital code, and the FSK Bi-Phase-M digital identification code is preferably redundant for data security during transmission and reception. 
     Further in accordance with the digital communication and processing aspect of present invention, the unique digital codes that are transmitted by each of the call boxes and received by the central station include both (i) an encoded identification of the individual call box that is transmitting the unique digital code, and (ii) a further encoded representation of a single message, one of a plurality of possible messages that are at different times transmitted from the call box responsively to different stimuli. The particular, preferred, messages that are encoded, and communicated, by the telemetry system in accordance with the present invention constitute a preferred method for the use of such system. The digitally encodable messages include one or more of the following: 
     (1) a manually generated request for transportation services, particularly a taxicab; 
     (2) an automated message indicating an abnormal condition, particularly including the abnormal conditions of motional perturbations attendant upon vandalism to the call box or a low power condition at the call box; and 
     (3) a periodic status report message in order that the on-line operational integrity of the call box may be verified. 
     In accordance with another aspect of the present invention, the telemetry system is improved in operation for recognition of plural messages when more than one is asynchronously transmitted at the same time. When communication&#39;s telemetry occurs, as is preferable for being economic of both equipments&#39; costs and the radio spectrum, upon a single narrowband radio channel, then the messages of a plurality of asynchronously operative call box transmitters may, and generally do, overlap in time and frequency. This overlap, or conflict, causes improper reception of conflicting messages at the central receiver. In accordance with the present invention, this message conflict is dealt with by causing that each of the plurality of transmitters should, upon each time that it does transmit its unique identification code and accompanying message, repeat the code and message a plurality of instances, nominally three times, within a short time interval. The cumulative durations of the plural transmissions are short in relation to the elapsed, real time, interval during which redundant transmissions are made, and are pseudo randomly distributed within such interval. Furthermore, the total number of call box transmitters within a telemetry system, and the maximum probable message frequency occurring at each call box, are configured so that it is of essentially certain probability that at least one of the redundant transmitted messages from each of the call box transmitters will be received at the central receiver. Further in accordance with this preferred method of redundant message transmission, the processing of the messages at the central receiver will ignore plural redundant messages received within the time interval during which the messages are redundantly transmitted. 
     In accordance with still another aspect of the present invention, the telemetry system is improved in the manner by which a positive response is given to a person registering a service request at one of the distributed call boxes. This positive feedback response to an initiated service request is efficiently without any involvement of the central station, and is efficiently without any communication from the central station to the call box, whatsoever. The present invention thusly obviates that the central station should incur the cost of a radio transmission capability, and that the call boxes should incur the cost of a radio reception capability. Particularly in accordance with the present invention, a call box is improved for providing a positive feedback response to a service request by incorporating a time delay circuit that is actuated by the user&#39;s registration of a service request. An indicator displays, after the expiration of a time delay, an indication to the user that the service request is acknowledged. In point of fact, the service request has been acknowledged, at least at the call box. However, the time delayed acknowledgement may, quite justifiably and by intentional design, appear to the user to positively indicate that some remote (time distant) agency, human or otherwise, has taken note of, and is in the process of responding to, the registered service request. With an acceptably high degree of certainty, this is indeed the actual case in the present automated telemetry system employing redundant message transmissions. The probability that a service request should be lost and that the positive feedback response to the initiator shall have been provided falsely is minute in relationship to other occurrences, such as traffic accidents, which routinely impede proper delivery of the requested service (normally taxicab transportation services) to the requesting user. Therefore the telemetry system in accordance with the present invention clearly renders a positive feedback response that is highly economical of generation while still being adequate, and normally highly accurate, so as to satisfy the user&#39;s concern that his/her request shall have been received, and is being acted upon. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a first level schematic block diagram showing the telemetry system in accordance with the present invention. 
     FIG. 2 is a second level schematic block diagram showing the CALL BOX component of the telemetry system in accordance with the present invention. 
     FIG. 3 is a second level block diagram showing the MASTER RECEIVER component of the telemetry system in accordance with the present invention. 
     FIG. 4 is a third level block diagram showing in greater detail the MASTER RECEIVER component of the telemetry system in accordance with the present invention. 
     FIG. 5 is a mechanical diagram showing the preferred physical organization of the MASTER RECEIVER component of the telemetry system in accordance with the present invention. 
     FIG. 6 is a first level program flow chart showing the program FASTCAB executed by the COMPUTER component of the telemetry system in accordance with the present invention. 
     FIG. 7 is a second level program flow chart showing the routine INITIALIZE within the program FASTCAB flow charted in FIG. 6. 
     FIG. 8 is a second level program flow chart showing the routine PROCESS CALL within the program FASTCAB flow charted in FIG. 6. 
     FIG. 9 is a second level program flow chart of the routine RESPOND TO MESSAGE TYPE of the program FASTCAB flow charted in FIG. 6. 
     FIG. 10a, 10b is a second level program flow chart of the routine PROCESS FUNCTION KEY of the program FASTCAB flow charted in FIG. 6. 
     FIG. 11 is a third level program flow chart of the subroutine DRAW SCREEN of the routine PROCESS FUNCTION KEY flow charted in FIG. 10a, 10b and of other routines. 
     FIG. 12 is a second level program flow chart of the subroutine PROCESS CURSER MOVE of the program FASTCAB flow charted in FIG. 6. 
     FIG. 13 is a third level program flow chart of the subroutine MOVE ARROW UP of the routine PROCESS CURSER MOVE flow charted in FIG. 12, and of other routines. 
     FIG. 14 a third level program flow chart of the subroutine MOVE ARROW DOWN of the routine PROCESS CURSER MOVE flow charted in FIG. 12, and of other routines. 
     FIG. 15 is a third level program flow chart of the subroutine MOVE PAGE UP of the routine PROCESS CURSER MOVE flow charted in FIG. 12, and of other routines. 
     FIG. 16 is a third level program flow chart of the subroutine MOVE PAGE DOWN of the routine PROCESS CURSER MOVE flow charted in FIG. 12, and of other routines. 
     FIG. 17 is a second level program flow chart of the routine PROCESS TIMED EVENTS of the program FASTCAB flow charted in FIG. 6. 
     FIG. 18 is a second level program flow chart of the routine TERMINATION SEQUENCE of the program FASTCAB flow charted in FIG. 6. 
     FIG. 19 is a first level program flow chart of the program FASTSET executed by the COMPUTER component of the telemetry system in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The telemetry system in accordance with the present invention is particularly directed to the digitalized communication and processing of service requests, particularly via digital radio and digital computers. The service requests that are digitally communicated and processed are asynchronously originated at ones of a large number of CALL BOXES. The nature of the service requests are, for example, to summon taxicab services and the CALL BOXES are situated at locations typically serviced by taxicabs. The CALL BOXES are particularly designed to be easily operated by the general public, and to give the operator-user a positive confirmation that the call has been made. The CALL BOXES are additionally capable of originating other digitally encoded messages including (i) disruption of the physical integrity of the CALL BOX by vandalism, (ii) low battery conditions, and (iii) periodic indications of operational integrity. 
     The digital messages that are asynchronously generated at ones of the CALL BOXES potentially conflict with each other on a single narrow band radio channel over which they are communicated, and prevent proper message reception at the central receiver. In order that each independent and asynchronous message and should be reliably received, each message transmission is repeated, typically three times. The duration, frequency of occurrence, and time separation of the repeated messages is such so as to ensure with a high probability that each message will be correctly received. 
     The digital messages are centrally received in a MASTER RECEIVER, or digital radio. The digital messages are then processed in a COMPUTER, typically a personal computer, operating under software program control. The computer processing of the messages allows recognition of valid, newly initiated, service requests while any extra copies of any one message which have been received due to redundant transmissions are discarded. The COMPUTER normally displays each incipient message requesting service to a human operator, who, responsively to the message, dispatches the requested service (typically a taxicab). The visual and printed displays of the computer are additionally capable of being provided directly to the attention of the service providers (the taxicab drivers) at some central dispatching location, or at remote locations if desired. The processing of, and optionally each response to, the service requests is cataloged. Cumulative records provide statistical information about system operation and the provisioning of services. 
     A first level schematic block diagram of the telemetry system in accordance with the present invention is shown in FIG. 1. A number of identical or substantially identical remote units, or CALL BOXES, 1000a through 1000n are geographically distributed. Each CALL BOX 1000 is battery powered for the transmission of digital radio messages, as is diagrammatically illustrated to transpire between CALL BOX 1000 and centrally located MASTER RECEIVER 2000. 
     One particular type of digital message typically transmitted by a CALL BOX 1000 is a manually initiated service request, typically a request for taxicab transportation services. The human registration of this service request is supported by the section OPERATOR INTERFACE 1100 of CALL BOX 1000. As is most particularly shown in detail for CALL BOX 1000 illustrated in FIG. 1, this section OPERATOR INTERFACE 1100 presents a convenient, simple, and friendly interface to the user. This OPERATOR INTERFACE 1100 is graphically identified to be a Taxicab Call Box, or the like, and typically consists of a brightly colored plastic bas-relief model of a taxicab. The sole user control is a brightly colored and illuminated push button switch 1102 prominently labeled &#34;PUSH&#34;. Directions for user operation are prominently displayed in an area 1104 adjacent the push button switch 1102. Such directions may be, for example, &#34;1. PUSH THE CALL BUTTON, 2. WAIT FOR THE LIGHT, [and] 3. WATCH FOR THE CAB&#34;. Graphical symbols such as a depiction of a finger pushing the call button, a representation of a &#34;CAB DISPATCHED&#34; light, and a representation of a person being picked up by a taxicab may respectively accompany the directions 1. through 3. At a predetermined time delay after the user presses the push button switch, the CAB DISPATCHED light 1106 will come on to indicate to the user that a taxicab has been dispatched. In actual fact this message only represents a highly probable occurrence, and it may be slightly premature in time to that actual instance when a cab is ultimately dispatched in response to the user&#39;s request. Nonetheless, the request-initiating user is pacified by the timely response to his/her service request while the system is constructed so as to allow reliable recognition of the registered request, and so as to permit reliable delivery of the requested service. 
     When the user depresses the push button switch 1102, a sequence of events occur within the CALL BOX 1000 resulting in transmission of a digitalized message via radio frequency (rf) signal. A DATA TRANSMITTER CIRCUIT 1200 and a TIMING &amp; CONTROL circuit 1300 are involved in the generation of this, and additional, messages. A RADIO TRANSMITTER 1400 produces the radio frequency signal that is encoded in accordance with the digital message. A BATTERY 1500 provides power to other electronic assemblies within the CALL BOX 1000. Each message from each CALL BOX 1000A-1000N contains a uniquely coded segment which indicates which particular one of the CALL BOXES 1000A through 1000N originated the message. 
     The centrally located equipments of the telemetry system in accordance with the present invention include a MASTER RECEIVER 2000 and a COMPUTER 3000 plus associated computer peripherals 3100-3300. The MASTER RECEIVER 2000 consists of a RADIO RECEIVER 2100 plus additional receiver components 2200-2700 that allow decoding of the received digital messages. Particularly, the RADIO RECEIVER 100 receives the radio frequency signal and provides an audio tone output to the DATA RECEIVER 2200. The DATA RECEIVER 2200, OUTPUT REGISTER 2300, INTERFACE MODULE 2400, DISPLAY 2500, SBC MODULE 2600, and ACIA MODULE 2700, decode the digital data from the received audio tone, and send the digitalized information to the COMPUTER 3000. 
     The COMPUTER 3000, normally of the IBM-XT or compatible types, operates under a control of a PROGRAM 3100 that resides in the memory stores of COMPUTER 3000 during normal system operation. The programmed operation of COMPUTER 3000 receives incoming digital messages from MASTER RECEIVER 2000, recognizes new messages, decodes the messages into quantities intelligible to humans (i.e., remote unit number and address, time of day, etc.) and causes display of these quantities on an operator interface, typically the SYSTEM OPERATOR MONITOR 3100. A system operator monitoring the quantities decoded from the messages may communicate with the computer for the logging responses to such messages via KEYBOARD 3200. The COMPUTER 3000 logs all received messages, and system operator response thereto, on RECORDER 3300, typically a flexible disk or a hard disk, for later statistical data processing and in order to provide a historical record of system operation. 
     A second level electrical schematic block diagram of the CALL BOX 1000, previously seen in FIG. 1, is shown in FIG. 2. When the faceplate lid (not shown) to the OPERATOR INTERFACE 1100 is opened, an abnormal occurrence usually resultant only during maintenance then the switch LID SW is closed causing a signal to be sent to POWER RELAY 1310. Meanwhile, a tilting or other physical disruption of the CALL BOX 1000 apparatus will cause closure of mercury switch HG SW 1120 providing a like signal to POWER RELAY 1310. It is for this reason that both the lid opening and the mercury switch signal are labeled VANDAL DETECTOR. Also received at POWER RELAY 1310 is a CALL DETECTOR SIGNAL resultant from the depression, or PUSH, of CALL SW 1130. Each of the CALL DETECTOR or the VANDAL DETECTOR signals causes the POWER RELAY 1310 to close, applying power from BATTERY 1500 to both RADIO 1400, DATA TRANSMITTER CIRCUIT 1200, and to the RADIO KEY TIMER 1320 of TIMING AND CONTROL 1300. The power from BATTERY 1500 is also provided through POWER RELAY 1310 to the LIGHT TIMER 1330. The LIGHT TIMER 1130 is a simple circuit gating power to LIGHTS 1140 after a predetermined time interval, typically a few seconds to 30 seconds. Illumination of the LIGHTS 1140 causes a message, typically &#34;CAB DISPATCHED&#34; to be visible within the WINDOW IN LID of OPERATOR INTERFACE 1100. 
     Continuing in FIG. 2 the TIME-OF-DAY-CLOCK 1340, which is resettable by the RESET switch, always receives power from BATTERY 1500. The clock is a simple elapsed time indicator providing an enablement signal for closure of POWER RELAY 1310 after a predetermined elapsed period, typically one day. Likewise, the LOW BATTERY DETECTOR 1350 also always receives power from BATTERY 1500. It provides a signal to POWER RELAY 1310 when a low power condition is sensed. The basic sequence by which all message transmissions are initiated is the same: basically the energization of the CALL BOX 1000 by closure of the POWER RELAY 1310, plus provision of such discreet control signals (not shown) to DIGITAL ENCODER 1210 as will permit the generation of a unique message. 
     Particularly, when power is applied through POWER RELAY 1310 to the DATA TRANSMITTER CIRCUIT 1200, a 16 bit digital code is generated. This code contains 4 binary bits, set or cleared in accordance with switches 1-4 AREA CODE, that represent the digitally encoded geographical area within which the particular CALL BOX 1000 is located. The code contains 8 bits, set or cleared by switches 1-8 STATION CODE, representing the unique identity of the particular CALL BOX 1000 within this particular area. It may thusly be recognized that up to 2 4+8  or 2 12 , i.e., 4096 different individual CALL BOXES 1000 may be uniquely identified. The remainder of the 16 bit digital code includes 1 bit representing a service request, or a CALL CODE; 1 bit representing the occurrence of vandalism, or a VANDAL CODE; 1 bit representing a low battery condition, or a LOW BATTERY CODE; and 1 bit representing a periodic message, or STATION REPORT CODE, generated responsively to the TIME-OF-DAY-CLOCK 1340. In response to a fixed frequency signal generated by the BIT RATE GENERATOR 1220, the DIGITAL ENCODER 1210 provides the 16 bit code to the frequency shift keyed FSK TONE GENERATOR 1230 to enable generation of a bi-phase modulated (Bi-Phase-M) digital code. The FSK Bi-Phase-M Digital Code, repeated for data security, is received as signal FSK TONE at RADIO 1400. 
     It is obvious that the message need not be limited to sixteen bits, that other and/or further meanings could be ascribed to existing and/or further message bits, and/or the information transmitted need not have unitary correspondence with the bits of the message but could instead be encoded into numerical values. The sophistication of message generation and informational encoding at the CALL BOX 1000 may readily be manipulated by a practitioner of the digital electronic arts. The preferred embodiment of the CALL BOX 1000, and the meanings ascribed to the message transmissions, may be varied while still conforming to the principles and spirit of the present invention. 
     The RADIO 1400, which now has power from BATTERY 1500 via POWER RELAY 1310, will transmit a radio frequency signal containing the information of signal FSK TONE via ANTENNA 1410 upon such times as signal BUSY received from RADIO KEY TIMER 1320 indicates &#34;not busy&#34;. At such time as signal BUSY from RADIO KEY TIMER 1320 indicates &#34;busy&#34;, then the RADIO 1400 will wait before retransmitting the information contained in signal FSK TONE. The RADIO KEY TIMER 1320 is controllable to produce a pseudo random delay by switches 1-4 1360. It is enabled to generate a predetermined number, typically 3, successive elapsed time intervals by closure of POWER RELAY 1310. The effect of the gated control of RADIO 1400 by the RADIO KEY TIMER 1320 for transmission of the information contained in signal FSK TONE effectively means that a predetermined number, typically 3, complete messages will be transmitted. Each message will have an actual &#34;on-the-air&#34; transmission time of 0.5 to 1 seconds. The overall telemetry system in accordance with the present invention employs that number of CALL BOXES 1000, and incurs that expected peak period message frequency at each call box, so as to permit that at least some ones of the (typically 3) redundant messages transmitted through RADIO 1400 during any pseudo random period will be correctly received at MASTER RECEIVER 2000 (shown in FIG. 1). At least one transmission of each independent asynchronously generated message from each simultaneously transmitting CALL BOX 1000 will be correctly received at centralized MASTER RECEIVER 2000 (shown in FIG. 1) even if some other ones of the message transmissions are not correctly received due to conflict, or overlap, between competing messages. 
     As well as enabling the energization of LIGHTS 1140, and the display of the message through the WINDOW IN LID, the LIGHT TIMER 1330 will cause that the lights are extinguished and that the POWER RELAY 1310 is disabled (by a signal the path of which is not shown) after a predetermined period, nominally about 1 minute since CALL SW 1130 was first pushed. Only after the LIGHTS 1140 have gone out, and after the POWER RELAY 1310 has been de-energized, can a new call originating at CALL BOX 1000 be registered. Prior to this time, if the operator user continues to push CALL SW 1130, then it will be considered that the successive actuations represent the same request originating with the same user, and no additional message will be dispatched. Such plural successive message transmissions (not counting the redundancy of each message transmission) as come to be dispatched from the CALL BOX 1000 may still be subject to an independent, autonomous, reasonableness and validity assessment by the telemetry system operator when the received messages are displayed on SYSTEM OPERATOR MONITOR 3100. In other words, a large number of closely time proximate messages originating at a signal CALL BOX 1000 may, or may not, represent an equivalent number of independent service requests. 
     A second level electrical schematic block diagram of MASTER RECEIVER 2000, previously seen in FIG. 1, is shown in FIG. 3. The RADIO RECEIVER 2100 receives the encoded digital radio signals originating at ones of the CALL BOXES 1000 via ANTENNA 2110. It converts the received radio frequency (rf) signal into tone information that is presented to the DATA RECEIVER 2200. The DATA RECEIVER is tuned to receive the particular frequency shift keyed (FSK) frequency tone that was generated by the DATA TRANSMITTER CIRCUIT 1200 of the REMOTE CALL BOXES 1000 (shown in FIG. 2). This tone typically has a center frequency of 2500 Hz and is shifted in accordance with binary message information by 100 Hz. The DATA RECEIVER 2200 is matched for decoding of the correct frequency, bit rate, and word length (typically 16 bits) that was generated by the DATA TRANSMITTER CIRCUIT 1200 of the REMOTE CALL BOXES 1000. 
     In response to the receipt of the FSK Tone from the RADIO RECEIVER 2100, the DATA RECEIVER 2200 produces a serial binary data string of 16 bits plus 2 end-of-word bits. This serial data string is validated for bit count, valid data bits, frequency, etc., and sent in parallel to the OUTPUT REGISTER 2300 and the INTERFACE MODULE 2400. The bit seal transmission transpires as signal DATA under control of shift pulses presented as signal SHIFT. The delayed signal DATA is looped back through the DATA RECEIVER 2200 from the OUTPUT REGISTER 2300 as signal LOOP. The LOOP signal feeds the bit serial data string representing the first message, or word, back into the DATA RECEIVER 2200 in order that it may be compared with a second message, or word, on a bit-by-bit basis. If, and when, successive messages are identical, then a pulse is transmitted as signal ACCEPT. This pulse is used to store the previously transmitted data in both the OUTPUT REGISTER 2300, and the INTERFACE MODULE 2400. This bit-by-bit comparison of an entire message, or word, constitutes a double scan of the data transmission. It is performed on all received messages. This redundancy helps to insure integrity of message transmission. 
     When the OUTPUT REGISTER 2300 receives the ACCEPT signal pulse, then the OUTPUT REGISTER 2300 is enabled for selectively illuminating respective indicators of DISPLAY 2500 in accordance with the message data stored within OUTPUT REGISTER 2300. The indicators are primarily for system maintenance and test purposes, and are not normally involved in system operation. System operation and control is normally performed via COMPUTER 300 (shown in FIG. 1). 
     The digitalized bit serial message received at INTERFACE MODULE 2400 is further passed to standard SBC MODULE 2600 and interface module ACIA MODULE 2700. The SBC MODULE 2600 and its companion ACIA MODULE 2700 produce an RS-232C interface signal containing the message information. This RS-232C interface signal information is transmitted as signal OUTPUT TO COMPUTER, which signal is routed to COMPUTER 3000 (shown in FIG. 1). 
     A more detailed, second level, electrical schematic block diagram of the MASTER RECEIVER 2000 (previously seen in FIGS. 1 &amp; 3) is shown in FIG. 4. A POWER SUPPLY 2050 supplies plus 12 v.d.c. plus 5 v.d.c. power to other modules. The signal S, and the return signal R, developed at RADIO RECEIVER 2100 are received at DATA RECEIVER 2200, typically of type DR3200 having industry standard part number 72-490. Similarly, the OUTPUT REGISTER 2300 is normally of type OR3200 having industry standard part number 72-370. The INTERFACE MODULE 2400a is typically industry standard part number 72-464 while the INTERFACE MODULE, SPECIAL VERSION 2400b is typically industry standard part number 72-567. The SBC MODULE 2600 is typically industry part number 72-567 and is tightly coupled as indicated to the ACIA MODULE 2700, also an industry standard component. 
     A suggested physical assembly of the modules within MASTER RECEIVER 2000, with each module identified by its part number, is shown in FIG. 5. As is therein observable, provision has been made for modular construction to facilitate maintenance and repair. A DISPLAY 2500 (shown in FIG. 3), consisting substantially of LED CKT BD 2510 part number 72-521 (shown in FIG. 4), visually displays the last message received. Certain system voltages and signals are additionally bought to terminals 1-10 of terminal block 2520, as desired, to facilitate test and maintenance of the MASTER RECEIVER 2000. 
     Momentarily returning to FIG. 1, it may be understood that the COMPUTER 3000, typically an IBM XT or compatible type, receives in digital form via the RS-232C interface from MASTER RECEIVER 2000 most, if not all, of the messages that are from time to time originated at various ones of the CALL BOXES 1000A-1000N. The COMPUTER 3000 operates under the control of software PROGRAM 3100. The flow charts of this software PROGRAM 3100 are the, subject of FIGS. 6-19. The PROGRAM 3100 operating within the COMPUTER 3000 will be operative, amongst other functions, to eliminate redundantly transmitted messages, to display all messages on the SYSTEM OPERATOR MONITOR 3100 in order that a human system operator may respond thereto, to receive system operator inputs via KEYBOARD 3200 and to log all system activities upon RECORDER 3300 (which is typically a hard disk). 
     One preferred computer program for control of the telemetry system in accordance with the present invention, wherein both the program and the system are particularly directed to the provisioning of taxicab transportation services, is the program FASTCAB which is flow charted in FIGS. 6-18. After entrance into the program proceeding from a bootstrap load of the program, or after entrance under computer operating system control, and after performance of initialization in block INITIALIZE 100 shown in FIG. 6, the program conducts all data and message processing by proceeding in a major loop. Within this loop the program FASTCAB will perform routines PROCESS CALL in block 300, PROCESS FUNCTION KEY in block 400, CURSOR MOVE in block 500, and/or PROCESS TIMED EVENTS in block 600, each and all routines as required. Until the program is terminated by manual intervention or by loss of power, the TERMINATION SEQUENCE of block 700 will not be entered, and the program FASTCAB will cycle continuously. 
     The detailed programmed operations occurring in the routines of blocks 100-700 of program FASTCAB (flow charted in FIG. 6) are generally shown in FIGS. 6-18. For example, the routine INITIALIZE in block 100 may be observed in FIG. 7 to consist of 8 different subroutines, shown within blocks 110-180. These eight subroutines essentially amount to preliminary housekeeping before commencing on-line system operation. Similarly, the routine PROCESS CALL of block 300 is shown in greater, flow charted, detail within FIG. 8. In a like manner to the tiered, detailed, flow charting of the major routines, some subroutines are also the subject of detailed flow charts. For example a subroutine RESPOND TO MESSAGE TYPE of block 360 which is within the routine PROCESS CALL of block 300, is further expanded in FIG. 9. The flow charts are substantially self-explanatory. For reference in interpretation, it should be understood the data element C$ represents a preliminary message staging, and holding, area. The data element B$ represents the historical array (or table, or list) of received messages. It may be particularly noted in subroutine RESPOND TO MESSAGE TYPE of block 360 (shown in FIG. 9) that a particular response will be made to each different message type which is received, from time to time, from various ones of the CALL BOXES 1000 (shown in FIG. 1). As well as the particular audible effects suggested by the names of boxes 362, 364, 366, (shown within FIG. 9) it will be understood that a visual display of the decoded message is presented to the system operator upon SYSTEM OPERATOR MONITOR 3100 (shown in FIG. 1). 
     Various function keys by which the system operator may typically interface with the operating program 3100 (FASTCAB) are shown in the flow chart of routine FUNCTION KEY of block 400 in FIG. 10. The assigned meanings of function keys F1-F8, and F-10 that are available on a personal computer KEYBOARD 3200 may be understood by reference to the flow chart. Most of the functions permit simple housekeeping, logging, and data entry relative to the succession of received messages. The subroutine DRAW SCREEN of block 450, used in the routine PROCESS FUNCTION KEY of block 400, is flow-charted in FIG. 11. 
     In a like manner, the major program routine of PROCESS CURSOR MOVE of block 500 is flow-charted in FIG. 12 whereas subroutines MOVE ARROW UP of block 510, MOVE ARROW DOWN of block 530, MOVE PAGE UP of block 540, and MOVE PAGE DOWN of block 550 that are used within this routine are variously flow charted in FIGS. 13-16. Final major FASTCAB program routines PROCESS TIMED EVENTS of blocks 600, and TERMINATION SEQUENCE of blocks 700, are respectively flow charted in FIGS. 17 and 18. A listing of the program FASTCAB that is flow charted within FIGS. 6-18 is attached as Appendix A to this specification disclosure. 
     It is desired to be able to perform a utility manipulation, for the purposes of data analysis and assessment, of the cumulative message files generated by operation of the program FASTCAB. It is additionally desired to be able to selectively initialize, display, and print such files. This utility manipulation is accomplished by program FASTSET which is flow charted in FIG. 19. The program, which has some routines and subroutines in common with the program FASTCAB, allows ready manipulation of the permanent historical record of system operation. The data so produced is available not only for assessing hardware performance but also for recognizing load factors, periodic patterns of occurrences, and traffic flows which may be pertinent to the temporal and spacial deployment of the transportation resources, mainly the taxicabs. The listing of the program FASTSET is attached as appendix B to this specification disclosure. 
     In accordance with the preceding discussions, obvious alterations and variations in the present invention will suggest themselves to a practitioner of the art of designing telemetry systems, and computer-based digital data processing systems. The digital message transmission and processing in accordance with the present invention is adaptable to other purposes other than the requesting of transportation services. For example, the digital messages and ensuing processing of such messages may reflect alarms or diverse matters other than transportation. The concept of the present invention that a user should be provided with a positive response feedback to his/her initiation of a message request without bidirectional communication of request and acknowledgement to and from a central station is obviously extendable to many telemetry systems receiving human-initiated messages at remote points, and wherein it is desired economize in the equipments, time, and radio frequency band-width used in the acknowledgement of such messages. Finally, the redundant message transmission in accordance with the present invention suggests alternative schemes for realizing reliable message receipt from a multiplicity of asynchronous originators of messages. Particularly, both time and frequency of multiplexing of message transmissions are more readily accomplished with modern digital technology than was priorly the case. In the case of time multiplexing, a broadcast of a central time coordination and marker signal may allow for the polling of call boxes at successive intervals, a particular interval being allowed for the response of each call box. The alternative use of frequency multiplexing records that the message communication of each asynchronous call box should be separately distinguishable in the electromagnetic spectrum, although this procedure requires extensive bandwidth and considerable sophistication in the receiving equipments, especially if a number of messages must be concurrently received. 
     In accordance with the preceding remarks, the present invention should be interpreted in accordance with the language of the following claims, only, and not solely in accordance with the particular preferred embodiment within which the invention has been taught. ##SPC1## ##SPC2##