RADIOTELEPHONE SYSTEM WITH CENTRAL OFFICE HAVING INDIVIDUAL PROCESSORS ASSIGNABLE TO RESPECTIVE MOBILE UNITS ABOARD COMMUNICATING VEHICLES

• US 3,729,595 A
• Filed: 02/04/1971
• Issued: 04/24/1973
• Est. Priority Date: 02/04/1970
• Status: Expired due to Term

• Current Assignee: Italtel SPA (Italtel Group SPA)
• Original Assignee: Luigi Sarati, Vincenzo Intini
• Inventors: Sarati, Luigi, Intini, Vincenzo
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): Kundert, Thomas L.
• Application Number:
  US05/112,562
• Time in Patent Office: 810 Days
• Field of Search: 179/41A,84VF 325/55,64,38,56,59,60 340/171PF 343/176,177,179
• US Class Current: 455/403
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 48/08 Access restriction or access information delivery, e.g. discovery data delivery signalling during connection H04W76/00
• CPC Class Codes: H04W 72/02 Selection of wireless resources by user or terminal
• CPC Class Codes: H04W 76/10 Connection setup

Abstract

A central office, designed for short-wave radiocommunication with mobile units aboard several vehicles in its area, has a plurality of fixed processing units operating on different frequency channels to communicate with various vehicle-borne mobile units in the area. Each processing unit includes a programmer (PG) which measures the response periods of a mobile unit to calling and switching signals transmitted by the central office and terminates the connection in the case of excessive delays. Each mobile unit has a transceiver tunable to any of these channels under the control of a ring counter (CA) which, on being started by an alert signal from the central office (in response to an incoming call) or by actuation of a hook switch aboard the vehicle (to initiate an outgoing call), drives the transceiver through all or part of a scanning cycle until a free channel has been found or until the search is halted by a concurrently actuated delay counter (CR). In either case, the ring counter locks the transceiver to the channel last explored until the next call is initiated. Each channel comprises two carrier waves modulated by a selected pair of audio frequencies out of a total of six such frequencies (f1 - f6) available for the transmission of numerical information in either direction; a seventh frequency (f7) is used in combination with two of the others (f5, f6) to pass switching or supervisory signals from the central office to the vehicle. If the call number of the mobile unit and/or of a station called from the vehicle includes two or more like digits in immediate succession, a repetition code (R) is substituted for the second, fourth etc. iterative digit to facilitate recognition of transition from one digit to the next.

Claims

1. In a radiotelephone system comprising a central office with terminal equipment, subscriber lines leading to said terminal equipment, mobile units aboard vehicles identified by individual call numbers and provided with transceiver means for establishing radiocummunication with said terminal equipment, and transmitreceive means connected to said terminal equipment for exchanging messages with said transceiver means over any one of a plurality of radio channels, in combination:

normally inoperative scanning means in each mobile unit for consecutively tuning said transceiver means to each of said radio channels in cyclic succession;

start means in each mobile unit operable preparatorily to the establishment of radiocommunication for activating said scanning means to explore successive channels for availability;

processing means at said central office connected to said transmit-receive means for emitting an availability signal over any channel not engaged in radiocommunication;

decoding means at each mobile unit for operating said start means in response to a call signal from said central office, said decoding means being further responsive to said availability signal for halting the operation of said scanning means;

first register means in each mobile unit for storing a first call number individual to such unit;

second register means in each mobile unit for storing a second call number assigned to a party to be called;

coding means in each mobile unit connected to said first and second register means for converting the stored call numbers thereof into frequency combinations transmissible by said transceiver means;

readout means at each mobile unit triggerable by said decoding means under the control of said start means for feeding the stored call number from either of said register means to said coding means for transmission of corresponding frequency combinations over a channel engaged by said transceiver means preparatorily to exchange of telephone messages thereover;

seizure means at said central office for sensing the presence of incoming radio waves on a channel and terminating said availability signal in response to such presence; and

timing means in said processing means for restoring said availability signal upon prolonged absence of incoming radio waves from a previously engaged channel;

said transceiver means comprising first and second mixer means for respectively modulating a first and a second carrier wave, said coding means including a source of several modulating frequencies for said carrier waves and logical circuitry for pairing said modulating frequencies in different combinations fed simultaneously to said first and second mixer means, respectively, said modulating frequencies having different numerical ranks assigned to them;

said logical circuitry including a preference circuit for invariably delivering the lower-ranking one of a pair of modulating frequencies from said source to said first mixer means and the higher-ranking one of such pair of modulating frequencies to said second mixer means.

2. The combination defined in claim 1 wherein said logical circuitry includes gating means for selecting any of the ten different frequency combinations for respective numerical digits in a multidigit call number and repeat-conversion means responsive to consecutive recurrences of the same digit in such call number for controlling said gating means to select an invariable eleventh frequency combination for every second consecutive occurrence of any given digit.

3. The combination defined in claim 2 wherein said coding means further comprises a sequencer including a digit counter, said sequencer having a multiplicity of outputs successively activable by said counter, said repeat-conversion means including a set of coincidence gates with input connections to respective pairs of adjoining sequencer outputs, at least one of said register means comprising a conductor array with a set of input leads respectively connected to said sequencer outputs and with a set of output leads intersecting said input leads and forming junctions therewith at intersections corresponding to respective digits, the presence of plural junctions on a given output lead short-circuiting the corresponding input leads along with the corresponding input connections of said coincidence gates.

4. The combination defined in claim 3 wherein said repeat-conversion means further comprises bistable means responsive to activation of any coincidence gate by a short-circuiting of its input connections for inhibiting a selection of said invariable eleventh frequency combination during an immediately following operating cycle of said digit counter.

5. The combination defined in claim 3 wherein said second register means comprises a store of carriers of said conductor array with differently distributed junctions representing different call numbers and preselector means for operatively connecting a single one of said carriers in circuit with said sequencer outputs.

6. The combination defined in claim 1 wherein said start means includes manually operable switch means and said coding means comprises a sequencer including a digit counter, said sequencer having a multiplicity of outputs successively activatable by said counter, said first register means comprising a logic matriX with input conductors connected to respective sequencer outputs and with output conductors intersecting said input conductors and forming junctions therewith at intersections corresponding to respective digits, said readout means including a discriminating circuit controlled by said switch means for modifying a final digit in a first call number stored in said logic matrix according to the position of said switch means thereby discriminating between incoming and outgoing calls.

7. The combination defined in claim 1 wherein said readout means comprises a programmer with a normally energized section, a normally de-energized section and a power supply for said normally de-energized section activable by said normally energized section in response to operation of said start means.

8. The combination defined in claim 7 wherein said programmer includes timer means connected to said decoding means for deactivating said power supply in the absence of said availability signal within a predetermined period after operation of said start means.

9. The combination defined in claim 7 wherein said programmer includes delay means responsive to prolonged absence of incoming radio waves from said central office for deactivating said power supply.

10. The combination defined in claim 1 wherein said processing means comprises an individual processor for each radio channel, said processor including a release circuit responsive to said timing means for generating a disconnect signal transmissible over the assigned channel to a mobile unit addressed via said assigned channel.

11. The combination defined in claim 10 wherein said release circuit includes a monostable element for limiting the duration of said disconnect signal.

12. The combination defined in claim 10 wherein said timing means comprises a bistable circuit with a relatively short setting time and a relatively long resetting time connected to said seizure means for setting and resetting in the presence and absence, respectively, of said incoming radio waves.

13. The combination defined in claim 10 wherein said timing means includes a monostable circuit for measuring the time elapsed between transmission of a call signal to a mobile unit and reception of a response signal over said assigned channel.

14. The combination defined in claim 10 wherein said timing means includes a monostable circuit for measuring the time elapsed between operation of said seizure means and reception of an invariable prefix of said first call number over said assigned channel.

15. The combination defined in claim 10 wherein said timing means includes a bistable circuit, a monostable circuit and a coincidence gate with one input connected to an output of said bistable circuit, another input connected to an output of said monostable circuit and a further input connected to a first signal source, the latter being also connected to an input of said monostable circuit, said bistable circuit having an input connected to a second signal source, said coincidence gate being nonswitchable upon a change in energization of said further input accompanied by a change in energization of either of its other two inputs.

16. In a radiotelephone system comprising a central office with terminal equipment, subscriber lines leading to said terminal equipment, a vehicle-borne mobile unit provided with transceiver means for establishing radiocommunication with said terminal equipment, and transmit-receive means connected to said terminal equipment for exchanging messages with said transceiver means over an available radio channel, in combination:

start means in said mobile unit for initiating communication over said available channel;

register means in said mobile unit for storing a multidigit call number instrumental in the establishment of such communication;

coding means in said mobile unit connected to said register means for converting the stored call number into combinations of frequencies simultaneously transmissible by said Transceiver means, with ten different frequency combinations assigned to the digits 0 through 9, said coding means including logical circuitry responsive to consecutive recurrences of the same digit in said call number for selecting an invariable eleventh frequency combination for every second consecutive occurrence of any given digit unrelated to the numerical value of such digit; and

readout means at each mobile unit triggerable by said start means for feeding said call number from said register means to said coding means for transmission over said radio channel to said terminal equipment.

17. In a radiotelephone system comprising a central office with terminal equipment, subscriber lines leading to said terminal equipment, mobile units aboard vehicles identified by individual call numbers and provided with transceiver means for establishing radiocommunication with said terminal equipment, and transmit-receive means connected to said terminal equipment for exchanging messages with said transceiver means over any one of a plurality of radio channels, in combination:

normally inoperative scanning means in each mobile unit for consecutively tuning said transceiver means to each of said radio channels in cyclic succession;

start means in each mobile unit operable preparatorily to the establishment of radiocommunication for activating said scanning means to explore successive channels for availability;

processing means at said central office connected to said transmit-receive means for emitting an availability signal over any channel not engaged in radiocommunication;

decoding means at each mobile unit for operating said start means in response to a call signal from said central office, said decoding means being further responsive to said availability signal for halting the operation of said scanning means;

first register means in each mobile unit for storing a first call number individual to such unit;

second register means in each mobile unit for storing a second call number assigned to a party to be called;

coding means in each mobile unit connected to said first and second register means for converting the stored call numbers thereof into frequency combinations transmissible by said transceiver means;

readout means at each mobile unit triggerable by said decoding means under the control of said start means for feeding the stored call number from either of said register means to said coding means for transmission of corresponding frequency combinations over a channel engaged by said transceiver means preparatorily to exchange of telephone messages thereover;

seizure means at said central office for sensing the presence of incoming radio waves on a channel and terminating said availability signal in response to such presence; and

timing means in said processing means for restoring said availability signal upon prolonged absence of incoming radio waves from a previously engaged channel;

said start means including manually operable switch means, said coding means including a sequencer including a digit counter, said sequencer having a multiplicity of outputs successively activatable by said counter, said first register means comprising a logic matrix with input conductors connected to respective sequencer outputs and with output conductors intersecting said input conductors and forming junctions therewith at intersections corresponding to respective digits, said readout means including a discriminating circuit controlled by said switch means for modifying a final digit in a first call number stored in said logic matrix according to the position of said switch means, thereby discriminating between incoming and outgoing calls.