Patent GB-476048-A (GB)
Title: Improvements in or relating to semi-automatic telephone exchange systems
IPC: H04M5/10
Filed: 1936-05-29
Abstract: 476,048. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., WRIGHT, E. P. G., and HARTLEY, G. C. May 29, 1936, No. 15228. [Class 40 (iv)] In a semi-automatic system, operators, particularly at a P.B.X with a large number of exchange lines, have cordless equipment comprising telephone equipment and a number of associating circuits each having supervisory equipment and adapted to connect the telephone equipment to any one of a number of similar conversational circuits. In one arrangement, Fig. 2, described in detail with reference to Figs. 3 to 5, an incoming call over junction J causes switch AS2 to connect up one of a number of supervision links SL which are connected in multiple to operator's telephone equipment ACT. When the operator responds, switch AS 1 connects up a key-sender KS and the call is set up over two-motion switches JS, IFS. Outgoing calls may be set up over LF, GS by subscribers themselves or subscribers may call an operator who sets up an outgoing call by dialling over the junction and sets up a connection to the calling party over JS, IFS as for an incoming call. The complete operator's equipment may be released as soon as a call is set up but by throwing a hold key in link SL, the link remains associated with the call for supervisory purposes. In a modification, Fig. 6, the supervisory link SL and junction switch JS are combined and connected to the junctions by AS2 which is now in the conversational path, the operator's telephone equipment being connected up by AS1. The Provisional Specification describes other modified lay-outs. Incoming call. Relay AC energized by ringing current operates BR which busies the junction to the group selectors GS for outgoing calls, marks the junction in bank asm28 of the associating switch ASM2 and operates start relay CS thereof over a chain start circuit. When the calling circuit is found, test relay CT operates CK which transfers the start circuit to the next switch, supervisory lamp SUL is flashed by intermittent ground on lead IEL and junction group lamp GL is lit informing the operator whether the call is from the main exchange or over a tie line. The operator throws key SK operating CSK followed by S which starts up switch ASM1 and when this switch reaches the position of ASM2, M operates in series with CA which follows when M shunts its high resistance winding. Relay MS pulls up and lights both line and group lamps LL, GL, the original circuit for GL having been opened by SK ; relays CH and CB pull up. The incoming line is now connected over aem24, 25 to the operator's telephone circuit OC which trips the ringing, and relays G and Z are operated. After enquiring the wanted number the operator sets it up on a key-sender as in Specification 476,088, which has been prepared by grounding lead GD, FZ being operated from the sender when the first digit has been stored. FZ operates RL which releases R and falls back, FZ being released on storage of the second digit whereupon lead STL is grounded to initiate sending. Vertical magnet VM of group selector JS responds to the first train over lead IL after which the sender grounds PAL to operate PA, thereby removing the ground from STL to stop sending and making a hunting circuit for RM. Test relay PT in the operator's circuit energized by an idle final selector operates PR which locks up and grounds lead STL so that the second digit is sent. At the group selector, HA has been operated from the operator's circuit followed by switching relay HB and the impulse circuit extended over jms6 to the vertical magnet of the final selector. At the end of the second digit ground on PBL operates PB releasing PRL to connect ground to STL whereupon the third digit is sent over aem12 and jsm5 to the rotary magnet and ground on PCL operates PC which disconnects ground from GD so that the sender restores to normal and PA, PB, PC relapse followed by PT. Relay CR in the link circuit, Fig. 4, has been operated by PC and locked. The wanted line is tested by ground at TPL, connected over a rotating switch to all supervision links in turn to prevent double connections, to relay CH(left), wiper jms4 and test wiper of the final selector which camps on busy lines, CH remaining unoperated and lamp SUL being flashed over lead FGL. If the speak key had still been thrown, continuous test ground is applied over cb4. If or when the line is idle, CH operates and locks. The wanted party is now rung over relay CF in the link circuit and the reply operates CF which releases CR and then falls back so that the operator is connected to the junction circuit and may speak to both parties. On restoring the speak key SK, the link circuit is released and G Z in the junction circuit relapse to connect LG to the called line whereupon L is looped across the junction, operates to main exchange feed and re-operates Z to switch the connection through, LG relapsing and leaving the windings of L and D connected in series in the junction wires. Testing for continued presence of calling party during a camp on busy line ; transfer of call to another P.B.X party. If the operator has restored key SK, CSK, CA, CB are released, and Z, Fig. 3, relapses, but G remains held in series with CK. Battery superposed on A.C. is connected to a simplex circuit over the junction. The battery holds the feed relay at the exchange, but if the calling party has released, the unbalancing of the circuit at the calling end as described in Specification 472,993 allows AC to operate whereupon HA, HB fall back and the circuits restore. If the operator is asked to transfer the call, she merely keys the new number, FZ and RL being operated as before when the first digit has been stored. RL releases HA, HB and makes a self-interrupting circuit for RM of the group selector which whereupon steps out and releases, RL then falling back. The new connection is then set up as previously described after the second digit has been stored. Holding the link circuit for supervision during conversation. If hold key HK is operated before SK is released, CHK pulls up and holds CK which maintains open the link start-circuit to relay CS. Release of SK releases CSK, S, M, CA and CB which disconnects the operator's telephone set. Switch AS1 is free to connect up the key-sender for another call, but if SK is re-thrown, CSK and S reoperate and AS 1 hunts until M, CA, CB operate as before. The operator can speak to either party to the exclusion of the other by throwing splitting key SX. Outgoing call set up by operator. The subscriber obtains the operator by means not shown, and the operator throws the speak key SK of an idle link together with a key GMK which marks the group of junctions or tie lines over which she desires to set up the call. CSK pulls up followed by OS and ASM1 hunts for an idle junction in the group marked in asm16. Battery on W5 at an idle junction circuit operates GT which causes ASM2 to step to the position occupied by ASM1, ASM2 being stopped by M which operates in series with CA. Relay CK pulls up, operates S and releases OS, whereupon MS operates and the line and group lamps LL, GL are lit. The operation of CA followed by CB energizes Z in the junction circuit so that BR pulls up followed by G. The operator releases key GMK, GT falls back, and she dials the wanted number, a connection back to the calling party being set up by using the key-sender, at any time during the setting up of the outgoing connection, in the manner previously described. Outgoing calls set up automatically by subscriber over group selector indicated at GS. When the junction circuit is seized, LG pulls up and loops L across the junction, whereupon Z switches through and releases LG, the windings of L being now connected in the wires of the loop from the calling party over the junction. HA operated by LG has locked up and operated HB followed by BR which busies the junction.