Patent GB-886279-A (GB)
Title: Improvements relating to automatic telecommunication switching systems
Inventor: WARMAN BLOOMFIELD JAMES
IPC: H04Q3/42
Filed: 1958-12-24
Abstract: 886,279. Automatic exchange systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Dec. 22, 1959 [Dec. 24, 1958], No. 41683/58. Class 40 (4). A group of lines has an associated start circuit comprising a calling line hunter which connects a calling line to the start circuit, which is thereby provided with the identity of the line, this identity being in turn signalled to a register which thereupon seizes a transmission bridge circuit and operates one or more line finders in accordance with the received line identity to connect the calling line via the transmission bridge circuit to the register. Fig. 1 relates to such an arrangement in a 1000-line exchange. As shown, when the loop L is closed the change of base potential of transistor TX1 operates the start relay ST which causes the line hunter F to operate. When the calling line is found transistor TX2 is energized to operate T which stops the switch and brings up TS, whereupon ST releases. Operation of ST also energizes the register hunting switch H. Two test relays TR, TB are provided, the first of which tests for a free register over H1 and the second of which tests over H2 to ascertain if the register in question has access to a free transmission bridge XB, busy contacts of all suitable transmission bridges to which a register has access being paralleled to the appropriate bank contact of H2. When both TR, TB operate the switch H is stopped and TFS comes up. With both TFS and TS operated, TT comes up to mark banks F2 and F3 whose outlets are connected in accordance with the tens and units digits of the calling lines to binary coders CT, CU, which thereupon transmit the codes to the register over the banks of H. The hundreds digit is also transmitted to the register over permanent strappings SF, it being assumed that the start circuit is associated with a single group of 100 lines. The register meanwhile seizes a free transmission bridge XB to which it has access and then sets line finders 2LF, LF by the revertive impulsing method, the reverted impulses being derived from contacts of bank I. When the line finders are set, K operates over the P-wire to release the start circuit. The register then receives the dialled digits via the transmission bridge and sets the selector train, which consists of a group selector and a final selector, by the revertive impulse method. The first line finder switch LF may also act as a final selector. Arrangements for larger exchanges.-These may be obtained by including a further stage of group selection or by the method shown in Fig. 5. Each 1000-line block such as A, B is provided with its own set of start circuits ST-A, ST-B and its own set of transmission bridges XB-A XB-B for calls within the blocks. For calls between the blocks there are provided extra transmission bridges such as XBX arranged to be reversible by means of contacts rr1, rr2. An incoming call gains access to a register as previously described, either via one of its own transmission bridges or via a transmission bridge such as XBX. When the dialled digits are received the register determines whether or not the calling and called subscribers belong to the same block or not and hence the type of bridge circuit required. If the call is at present coming in over the wrong type of bridge circuit, the register hunts for a bridge circuit of the correct type and sets up the call over it, dropping the original bridge circuit. Appropriate operation of RR is effected by the register. Inter - exchange calls.-Incoming junctions connected to a first selector at the previous exchange may be treated in the same way as local lines. Others may be provided with individual bridge circuits containing a digitstoring device for storing the first digit whilst a register finder is connecting the transmission bridge to the register, Fig. 4 (not shown). Fig. 6 illustrates an arrangement having both incoming and outgoing junctions. Each incoming relay set is provided with a register hunter HJ as well as a digit storage device DS. The register receives the identity of the incoming junction and the incoming dialled digits over switch HJ. According as the call is for an outgoing junction or is a local call, the register then seizes either bridge XBJ or bridge XBL and sets the appropriate selector train and junction finder JF in accordance with the information in its possession, to complete the call.