Patent GB-409296-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone or like exchange systems
IPC: H04Q3/00
Filed: 1932-10-25
Abstract: 409,296. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., WRIGHT, E. P. G., HARTLEY, G. C., and ROBERTS, G. A., Connaught House, Aldwych, London. Oct. 25, 1932, No. 29797. [Class 40 (iv).] At a satellite exchange equipped with finderconnector links for setting up local calls and provided with main exchange junctions and tie lines terminating in finders which serve alternatively as finders and connectors, all connections are controlled by common bypath circuits which act differently according to the type of call to be established. Fig. 1 shows the lay-out for a 200 line exchange in which the finders and connectors each comprise two switches which are used alternatively according as the subscriber is in the odd or even hundreds group. Each bypath BPC comprises the usual R1, R2 switches and is associable over a switch PF with local circuits PC, junction circuits JC, tie line circuits TLC and a revertive call circuit RC. A locally initiated call is extended through PC to the bypath by F1 or 2, R2 seizes a junction and R1 discriminates in response to the first or first two digits, which are sent over the junction. If the call is a local one, the junction is released and the call is completed over S or 2. If the call is to the main exchange, SF1 or 2 is set to the calling line and the bypath and local link are released. If the call is to an adjacent exchange, the junction is released, R2 selects a tie line, TF1 or 2 is set and the bypath and local link are released. Should there be no tie line available, the call is routed via the main exchange. A revertive party-line call is set up over RF 1 or 2 like a tie line call. The revertive call circuit also serves to extend a calling line to the bypath when all the local links are in use : local calls cannot be established however. On incoming calls three digits may be received or two digits plus a signal discriminating between the odd and even hundreds groups. In the former case a relay is operated in the bypath to enable R1 to respond to the preliminary digit. The main exchange operator is able to break down an existing local or short toll call in favour of a call of greater importance. A somewhat similar layout for the main exchange is shown in Fig. 9. Incoming call from main exchange. Relay AX, Fig. 5 energizes over the junction in series with AV (in operative), and connects up SV which operates JA in the common start circuit and connects battery to lead T. Start relay ST, Fig. 4, energizes in each idle by-path and the switches PF hunt for the junction. When this is found, test relay PT pulls up in series with 1C, followed by PH, PP, F, FH. The switch R2 if off-normal goes home and JT pulls up. FH earths lead KS to operate K and hold SV, while K earths the negative lead to operate impulse relay A, Fig. 4 which controls release relay B. Relays BJ, AB, KK energize and the switch MF, which serves as a sequence switch, moves to position 1, in which relays D, TB energize, and PT, PH, Fig. 4, fall back, whereupon BB pulls up and disconnects start relay ST. Relay AX is now short-circuited by contact d1, and the junction is switched through to the register-controller at the main exchange. Relay AJ operates over the junction and releases SJ, whereupon impulse relay A is placed under the control of AJ. If the call is for a subscriber in the odd hundreds group, the feed over the junction is reversed, and relay BT (shunted by a rectifier) responds, operating Q, P to connect up the switch SF2 in place of SF1 and J in the by-path. Impulses received over the junction are repeated by relays AJ, A, and the tens digit steps the switch R1, JT falling back at the first step to allow the switch R2 to chase R1. Dialling relay C on relapse connects up change-over relay E, and R2 steps in response to the units digit. Relay C on pulling up releases F and on falling back operates TD, which connects up R, Fig. 5 over lead GS, whereupon MF steps to position 2 in which WJ energizes and D falls back. Relay AX being no longer shortcircuited re-operates, while AJ falls back, BJ and A now being held by AX. Relay H, Fig. 4 energizes and connects XP to common guard resistance MKG which is such that only one XP relay can be operated at a time to prevent more than one bypath using the marking multiple simultaneously. When XP energizes, X pulls up and the switch SF1 or 2 (dependent on Q) steps to the wanted line marked over rm 24 or 25, when M energizes followed by G, which closes the test circuit over leads HS, H to relay FT pending the relapse of TD. Called line idle. FT energizes to battery on lead HS, connects up SW to hold TD and short-circuits its high resistance winding, whereupon K, L operate in the line circuit, Fig. 2. FT falls back and switching relay HJ energizes and connects lead HS to earth through TB in the case of a short toll call. In the case of a long toll call however, the junction is opened for an instant before switch-through occurs at the distant end, and relay MS has time to operate before AJ, so that lead HS is now earthed directly. Lead MR is earthed. GJ pulls up and disconnects A to release the bypath. R1 goes home, while R2 advances to position 30 in order to save time when it is required to search over junctions and tie lines which are wired to its later positions. MF, Fig. 5 moves to position 3 in which earth is connected to lead RTL to initiate ringing, which is applied over leads RRL, IRL. Ring trip relay FJ operates on reply and releases WJ, R, and back-bridge relay D pulls up and shortcircuits AX to give supervision. AJ energizes and holds release relay BJ. MF moves to position 4. Upon release at the distant end, the junction is held by a relay controlled by two line relays each connected between one wire and earth. BJ falls back and MF goes home, whereupon EJ, EE energizes and apply battery through BT, AJ to each junction wire to release the junction. VJ pulls up and the circuit restores to normal. Called line unequipped. Lead HS is disconnected so that FT, SW do not operate and TD, H, M fall back. The switch SF1 or 2 advances again and stops in position xx when M operates over dead line marking lead DL. Relay HJ energizes and switches through to NU tone equipment, which returns battery on one wire to operate FJ and release WJ, R. The by-path is released. The operation is the same if a permanent loop exists on the line, since lead HS then includes a high resistance. Called line busy. FT, SW do not operate and TD falls back, while BU energizes to earth on lead HS before H falls back and releases M. R, Fig. 5 relapses and MF steps to position 4, in which VJ, XJ pull up, disconnecting A to release the by-path and stepping MF by means of pulses over lead IEL, TB being short circuited over wiper mfm1 by full earth on lead HS in position 5, on lead MR in position 8 or directly in position 11 according as the subscriber is engaged in a long toll, short toll or local call. TB disconnects WJ to stop MF and busy tone is applied to the junction from lead BTL. Breaking down local or short toll connection. The main exchange operator rings, operating CJ (shunted by a rectifier) and CC, whereupon MF moves to the next position 6, 9 or 12. In 6 and 9, distinctive tones are applied from leads LTL, STBL to indicate the nature of the existing toll call, while in 12, ordinary busy tone is applied. The operator cannot break into a long toll call, since further ringing has no effect on MF. In the other two cases, however, further ringing advances MF to position 10 or 13, in which TO pulls up,and MF continues to position 15 in which relay HJ switches through and the call is offered. If necessary, a third application of ringing drives to MF to position 16 in which full earth is applied to lead HS to release the existing connection by short-circuiting a relay corresponding to TB, and thence to position 17 in which the subscriber is rung. P.B.X. hunting. Lead PBF is multipled to the positions of wipers rm26, 27 corresponding to the first lines of P.B.X. groups, which are denoted by the tens digit 1, 3 or 5, while lead PBL is multipled to the positions corresponding to the last lines. V energizes when the test circuit is made, holding TD and R2 goes to the last line of the group, when JT pulls up and releases V. Meanwhile M falls back and the switch SF1 or 2 advances over the group, each line being tested by FT. M energizes on the last line and if this is busy, a busy signal is given as described above. Local call. Line relay L, Fig. 2, marks the calling line over lead HF and connects up SA, which starts the switches PF hunting as for an incoming call. Separate start circuits are' provided for the odd and even hundreds groups and a switch PF may seize the same link in either of two consecutive positions dependent on which SA relay is operated. Relays PT, PH, PP energize, and the appropriate finder F1 or 2, Fig. 3, steps to the calling line, when FT energizes over lead H1 or 2 and HF in series with cut-off relay K. SW pulls up, and FT falls back when the marking is removed and connects up FH. If the subscriber is in the odd hundreds group, PS energizes over lead KS2, switches over to the finder F2 and connects up KS, while if he is in the even hundreds group, KS energizes over lead KS 1. Release relay BS energizes followed by RS, which extends the loop to impulse relay A, Fig. 4. Release relay B pulls up. R2 steps in search of an idle junction marked by battery on lead T, Fig. 5, when JT pulls up. Relays W, WT control the advance of RI to position 27 or 39 according as local numbers have 4 or 3 digits ; in the present instance it is assumed that they have 4. Certain pairs of wipers of R1, R2 are connected together to serve as sequence switches, and their contacts are shown in Fig. 4 as small circles bearing the wiper numbers, with small numerals to indicate the closed position. Relays EJ, EE, Fig. 5, energize and connect battery to each junction wire through AJ