Patent GB-760927-A (GB)
Title: Improvements in or relating to electrical signalling systems
IPC: H04W88/02
Filed: 1953-08-26
Abstract: 760,927. Intercommunication systems. ERICSSON TELEPHONES, Ltd., POLLARD, J. R., STRINGER, J. T., and TAUB, D. M. Aug. 26, 1953, No. 23504/53. Class 40 (4). [Also in Group XL (c)] A central station RT, Fig. 1, calls a substation by transmitting A.C. impulses to all substations over radio links or physical circuits. Impulses are counted by a single multicathode gas discharge tube. The impulses are generated by a dial controlled oscillator OSC. A substation RR responds to a number of impulses signifying either the station or a group of stations. At the substation, the impulses are detected by a responder IR and are counted at IC. A discriminator DS responds only to a number identifying the station or a group and operates a switch CR to give a calling signal. If both radio links and physical circuits are used in the same system, the A.C. impulses are transmitted to both over separate contacts of the same relay. In two embodiments described, the substation responds to 9, 47, 49, the individual number of the substation being 47. All stations respond to 9 and a group of stations responds to 49. Receiver, first embodiment, Figs. 3, 4, 5. The incoming A.C. on terminals X3, X4, Fig. 3, is applied to a valve V1 and the output in the tuned anode circuit is rectified, smoothed and fed back as a grid bias to increase the anode current and to operate control relays A, B. Relay A follows the impulses and dialling relay B made slowto-release by rectifier MR2 falls back only at the end of a digit. A multi-cathode discharge tube, Fig. 4, described in Specification 712,177, [Group XL (a)], or 712,215, is used to count the impulses repeated by A. Counting electrodes H, S1 ... S9 are arranged in a circle around the anode and guide electrodes GD1, GD2 are arranged in pairs between successive counting electrodes only one pair being shown. All the guide electrodes GD1 are commoned to one lead and the electrodes GD2 to another. The discharge is stepped from a first electrode to an adjacent electrode when the adjacent electrode is made more negative than the first electrode. Normally, a discharge invests the home electrode H. When relay A repeats an impulse, a negative pulse from battery N1 is applied through condenser C5 to guide electrode GD1 first and then, after a delay due to resistor R4 and condenser C6, to guide electrode GD2. Finally, as the pulse dies away both GD1, GD2 return to their normal condition which is positive with respect to H and the discharge meantime steps from H to GD1, GD2 and S1. Each impulse advances the discharge by one counting electrode. When B falls back at the end of a digit, the negative pulse over b returns the discharge to the home electrode H. In the discriminator, Fig. 5, valves V2 to V5 are normally biased to cut-off. Leads from the cathodes S1 to S9 are connected to valves V2 to V5 through delay circuits such as R19, C8 so that a conductive electrode can build up an enabling potential on a valve only if the discharge persists longer than an impulse, which it does before B falls back at the end of a train. In the circuit shown, the numbers 47, 49 both operate valves V2, V4 and relays D, F which lock. At contact F3 a lamp, bell or loudspeaker is operated until relays D, F are released by key KA. A single digit 9 operates V4 and F with the same results. Two-digit numbers other than 47, 49 operate either D, G or E, G to return the discriminator to normal by opening contact G1. Receiver, second embodiment, Figs. 6, 7, 8. The relays A, B, the multi-cathode discharge tube and the thermionic valves V2 to V5 of the first receiver are all replaced by gas discharge tubes. At the end of each impulse on terminals X7, X8 a positive pulse is fed from the resistor R33 in the anode circuit of V6 to gas discharge tubes DT2, DT3. Tube DT2 strikes momentarily and, transmits a short positive pulse to terminal L1 of the counter, Fig. 7. Tube DT3 which is normally conducting, is extinguished by a negative pulse from V6 at the beginning of an impulse and does not strike again until the end of a digit when there is time for the striking potential to build up over the delay circuit R30, R37, C21. A pulse from the cathode of DT3 is applied to terminal L2 of the counter and strikes DT4 to prepare the counter. Subsequent pulses on terminal L1 are counted in known manner by tubes DT5 to DT14 and at the end of the digit DT4 is again operated in readiness for another count. The cathode potentials on the counting tube prime discriminator tubes DT15 to DT18 through rectifier gating circuits. A primed one of the tubes DT15 to DT18 strikes at the end of a digit count when anode potential is applied to terminal L8 from DT3. Any one of the tubes DT15 to DT18 previously conducting is extinguished as the primed tube strikes. The digits 4, 7, 9 control the potential or terminals L3, L4, L5 and other digits control terminal L6. Tube DT15 is normally conducting and opens gates MR35 to MR38, gates MR31 to MR34 being opened when DT17 strikes. Digit 9 strikes DT18 and gives a calling signal across terminals X9, X10. Digit 4 strikes DT17 and 7 or 9 following to strike DT18 to give the signal as before. Following the digit 4, any digit other than 7 or 9 strikes DT15 and returns the discriminator to normal. Any first digit other than 4 or 7 strikes DT16 which in turn strikes DT15 over rectifier MR30. When a calling signal is received it can be terminated by momentarily operating switch SW.