Patent GB-417202-A (GB)
Title: Improvements in or relating to carrier current signalling and distant control systems
IPC: H04M7/16
Filed: 1933-04-03
Abstract: 417,202. Wired - wireless systems. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and WESTELL, E. P. L., c/o General Electric Co., Stoke, Coventry. April 3, 1933, No. 9942. [Class 40 (v).] Three or more carrier systems are interconnected via suitable modulating and demodulating apparatus by a common coupling apparatus which comprises only direct current apparatus with or without low frequency apparatus and is adapted to repeat selective or control impulses and, if desired, speech between any two carrier systems. The carrier systems utilize power networks or telephone lines and where telephone lines are employed speech is preferably transmitted without using a carrier. The system shown in Fig. 2 comprises three stations 1-3 connected over carrier channels to the coupling apparatus C. The stations have a number of extensions comprising supervisory or control points or telephone extensions, and the station switching equipment may be as described in Specification 395,053. A further station 4 may be coupled to station 3 by apparatus as described in Specification 395,045. One or more telephone extensions 6 may be directly connected to the coupler C. The coupling circuits, Fig. 2, are associated with terminal apparatus of the carrier systems shown in outline at the top of the Figure, and comprise a register-controller (switches D.H) for storing and re-transmitting impulses, a finder F which hunts for the calling system, and a selector D which is stepped to the wanted system. Connections to and from the telephone extension shown are set up in a similar manner. Call from system 1 to system 3. Incoming calling current operates a relay (in a manner not shown) to close cx and energise 1A, whereupon 1B pulls up and energizes S which causes sequence switch J to take one step and makes a hunting circuit for F, bank F2 of which is marked by removal of a short circuit on relay 1EX. When the calling system is found 1EX holds S, H and K pull up, while DT vibrates by selfinterruption and supplies dialling tone over F3. Relay BX also pulls up in series with AX the purpose of which is to control the transmission of carrier signals back over system 1. The calling extension now dials impulses which after transmission over the carrier channel are repeated at cx to 1A which repeats them to dialling relay C and switch D in parallel. C causes J to take a further step to contact 2 and, assuming a first digit 0, D proceeds to contact 10 where C is held. The second digit (say 4) takes D to 14 and C falls back so that J steps by self-interruption to contact 22. Relay 3N pulls up over D2 and operates the transmitting relays AZ, BZ, of system 3 to send out calling current, and relay P pulls up to complete a two-way speech path between the two carrier systems over F3, D4, and F4, D3 and intermediate transformers T1, T2. When the ready signal comes in from the distant carrier terminal of system 3, cz operates 3A and 3B completes a circuit for X over J4 so that an impulsing set X-Z starts up and Z sends selecting impulses to AZ for transmission over system 3 and also impulses a sending switch H over J2, C also operating to step J to position 23. When H2 reaches the contact marked over D6, battery over these wipers causes J to take a further step whereupon impulsing ceases and LO pulls up to complete two-way impulse signalling circuits. The selecting impulses sent over system 3 may, by suitable cross-connections between H2, D6, be a translation of the dialled digits. Signalling from system 1 to system 3 is now effected by R which is impulsed over F5 by 1A and repeats to AZ, and in the reverse direction by T which is impulsed over D5 by 3A which repeats to AX. Busy signal. If system 2 attempts a call during the above described connection, 2A, 2B pull up but since H is operated Q and ET are energized. Q operates AY, BY to send a reply signal over the calling system while ET vibrates and tone over its lower winding passes to the output transformer to system 2 to modulate the signal thereby indicating a busy condition. A similar signal is given if system 3 attempts a call while 1 is in the process of calling but in this case the operation of relay 3N when the wanted number has been registered removes the tone. Release. 1A falls back followed by 1B and 1EX relapses to release S which completes homing circuits for the various switches. Call to telephone extension directly connected to the coupling apparatus. F hunts for the calling carrier system as before, and D is set by incoming impulses (6) on to contacts of the extension shown. In this call, the intermediate transformers are not required, so that when 4N operates over D2, P remains unoperated but 4N connects up potential for operating the extension bell. When the extension replies, W pulls up, disconnects the ringing circuit and causes J to step over J3 to position 24 where LO operates as before. A speaking circuit is now complete from microphone EM over D3 to a feed choke and thence over F3 to the outgoing transformer of the carrier system, while the circuit in the other direction passes from the incoming carrier transformer over F4, D4, to the receiver ER The telephone extension may then signal over the carrier channel by the operating dial the impulses being repeated by T to AY. If the extension has a supervisory or control unit it may be controlled from the carrier system by impulses repeated by 2A to R.