Patent GB-305731-A (GB)
Title: Improvements relating to telephone systems
IPC: H04Q3/42
Filed: 1927-11-17
Abstract: 305,731. Siemens Bros & Co., Ltd., and Christian, D. A. Nov. 17, 1927. Automatic and semi-automatic exchange systems. - In a system comprising automatic and manual exchanges and in which calls from, or proceeding through, an automatic exchange to a manual exchange are displayed on a call indicator at the manual exchange, the wanted number is transmitted over a circuit (order wire) independent of the conversational junctions. The circuit may comprise several conductors so that difficulties of signalling over a two-wire junction are avoided. In the system described, the manual 'exchange code comprises two digits, the first of which designates that the call is to a manual, exchange. A first group selector (not shown) is stepped in accordance with. the first digit to a level having access to links CF, JS, J, Fig. 2. leading to junctions to manual exchanges. A switch CF in the first idle link hunts for a coder CA in which registers MF, M, H, T, U, Figs. 4 and 5, are set by the remaining digits. The first of these, registered in MF, determines the exchange to which the call is to be directed and one bank of MF is cross-connected to a bank of a hunting switch OF, a further bank of which is cross-connected to a bank of distributor DD which routes the impulses to the various registers. When registration is complete, a switch MM of a group allotted in turn to deal with waiting coders, is stepped until it reaches contacts connected to the marker contacts in MF when it marks a contact in the bank of switch SM. This switch now steps off and, when it arrives at the marker contact, switch OF is started up to hunt for the order wire or group of order wires which has been marked by the cross-connection between OF7 and MF5. The arrangement just described ensures that waiting coders are dealt with in the order in which they are taken into use. The conductors V - - Z of the order wire are now extended to a sending switch PS and the digits are transmitted from the numerical registers M, H, T, U to the lamp indicator LI, Fig. 8. The operator inserts the plug of a cord-circuit C, at the incoming end of a junction, into the jack of wanted subscriber's line and a signal is sent back over the junction to equipment J which marks the junction in the banks of junction selector JS, the levels of which are connected to groups of junctions outgong to various manual exchanges. This signal also effects circuit changes in equipment OX, Fig. 7, to start the transmission of impulses, in accordance, with the setting of MF, to the junction selector which is stepped to the level containing the marked junction and hunts over the level. The impulse circuit is completed in one position of PS and the impulses are counted by DD by virtue of the cross-connections between MF, OF and DD. When the junction selector has switched through, the coder is released. Code-translating register-controllers may be modified to provide the facilities required by the invention, or additional apparatus may be associated with existing register-controllers. Modifications are referred to in which (1) an idle junction of a group may be selected at the automatic exchange, the manual operator being advised by a lamp signal (2) the number of the junction selected by the manual operator may be transmitted back, preferably in code, over the order wire to set the junction selector at the automatic exchange. The stepping relays M, Fig. 4, and XB, Fig. 6, of switches OF and MM are differentially wound, the interrupter contacts of the magnets being included in the, circuit of one winding so that energization of the magnet in a circuit including a. back contact of the relay opens one winding to permit the relay to pull up and open the circuit of the magnet. Operation of link-circuit, Fig. 3, and selection of idle coder, Fig. 4 and 5. When an idle linkcircuit., indicated by battery over off-normal contact k1, is seized by the first group selector, impulse relay A energizes N (1) which holds open the speaking wires to junction selector JS until the assigned junction has been found and at w1 closes a holding circuit for itself, the impulsing circuit for the coder being prepared at n4. The coder selector CF has no normal position and if it is resting on an idle coder, its test relay T will pull up over w2, w3 in series with magnet CDM. If it is not, T is short circuited by busy ground at b2 in the coder over wiper CF3 and magnet CDM steps the finder on to an idle coder. Relay T at t1 connects ground from wiper CF1 to CF3 to busy the coder and at t2 extends ground from the c wire over CF6 to the release relay B of the coder which returns busy ground from b2. The impulsing circuit over wiper CF2 is completed at t3. All coders busy. The end contacts of switch CF are not connected up to coders but ground from idle coders is connected over contact b3 of the release relay B to a common wire I leading to an end contact of wiper CF3. When wiper CF3 is stepped on to this contact and no idle coders are available, test relay T operates and at t5, t6 connects up busy signal from BB over wiper CF5 to notify the calling subscriber. Registration of digits. The second digit is repeated at a2 over wire 2, relay C, wiper DD2 and first contact of distributor DD, b5 to magnet MFM which sets register MF. Relay C operates in this circuit and at c1 closes a circuit for slowto release relay DS. At the end of the impulse train C falls back and is followed by DS but in the interval a, circuit is completed over b1, c1, ds1, and wipers DD5, DD1 for magnet DDM which, when its circuit is broken at ds1, steps the d: stributor to its second contacts. The thousand digit is now repeated over DD2 and wire 7 to register M and switch DD is stepped to its third contacts. The remaining digits are similarly recorded on registers H,T, and distributor DD is stepped to its sixth position. In the fifth position of DD and during the release period of DS, relay E, Fig. 5, energizes over ds2, DD4, c1, b1, locks up over e1 b4, t6 and psm, and at e2 connects battery over wiper MF2 and wire 52 to mark the waiting coder in bank MM1 of marker MM. Dealing with waiting coders in equitable order; selection of idle order wire V - - Z. A group of markers is provided for each manual exchange accessible to a coder, the markers of a group being brought into use in succession by an allotter such as AM individual to the group. A marker is not stepped off until one previously allotted has found a waiting coder and when this occurs, and if or when there is an idle order wire, switch SM rapidly searches for the first marker to start an order wire selector OF. In the sixth position of distributor DD, ground from b1 is connected over DD4, MF1, 51, and relay XA to magnet ADM of allotter AM which does net operate. This circuit branches over xb1, AM4 to marker magnet MMM. Relay XA locks up over xa1, and at xa2 completes circuits for windings 1 and 2 of relay XB which, being differentially wound does not operate. The circuit for XB (2) includes the contacts mmm of magnet MMM which, on operating, breaks the circuit of XB (2) so that XB operates and breaks the circuit of MMM. This interaction continues until MM reaches the above-mentioned marked contact in MM1 when relay MB operates in series with XB (3) and connects ground from mb1 over MM1, MF2, c2, e3, DD3 to magnet DDM which steps DD to position 7. Relay XA is short-circuited by ground over mb3 and falls back to connect this ground to magnet ADM which steps the allotter to the next-idle marker. In position 7 of DD, battery is connected over DD6, e4, MF3, MM2 to a contact of switch SM. Relay MB also connects ground from ga4, Fig. 7, of an idle order wire over za1, Fig. 6, to magnet SDM and ZA (1) which, however, is short-circuited by contacts sdm of the magnet. Interaction between SD11-T and ZA ensues until ZA holds in a circuit from battery on the marker contact of SM over za 1, ZA (2) to ground at ga4. A circuit for the magnet OFM of OF is now completed over m1, OF1, DD6 in position 7, e4 and the previously traced circuit over MM2 to ground at go4 which is further connected over m1 to relay M (1), Fig. 4, and over OF1, ofm, to M (2). Relay M being differentially wound does not operate until the circuit of M (2) is broken at the magnet contacts ofm, when it pulls up and opens the circuit of OFM. After OF takes one step, the circuits for OFM and M pass over OF1, st2, t1 and relay RA. Idle order wires are marked in OF6 by battery over relay GA, Fig. 7, and as the circuit of test relay T (1) of OF passes from ground at e5 over wiper MF5 of the register MF to OF7 and OF6, the switch is stepped on until an idle order wire to the desired exchange is reached, when T pulls up in series with GA and holds over winding 2 in series with OFM which does not now operate owing to the high resistance of T (2). Ground from gn holds relay GA and busies the order wire. The conductors W, X are now connected over t2, t3 to PS3, PS4. Relay M (3) is short circuited at t4 and falls back. A holding ground is connected at t5 for release relay B and at t6 a circuit from ground at psm is closed for relay DS (2), Fig. 5, with a parallel circuit over PS1 for relay N. Transmission of wanted number to call indicator, Fig. 8, and display of number. Wipers PS2 - - PS5 of the sending switch PS are now connected over OF2 - - OF5 and the order wire to relay sets at the indicator, and magnet PSM and relay N interact to step PS. In positions 1 and 2, weak battery over PS3 and W operates relay L, Fig. 8, and relays B, H pull up in succession, lamp CL being lit to signal to the operator. Conductor V of the order wire is connected over h1, rh2 to relay MA and the other conductors W-Y are connected over rh3, rh4, rh5, to relays MB, MC, MD. In position 3, the thousands register M is connected to the order wire and, according to the setting of its wipers M2, M3, battery is connected to one or more