Patent GB-352529-A (GB)
Title: Improvements relating to telephone systems
IPC: H04M5/08
Filed: 1930-04-08
Abstract: 352,529. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, CHRISTIAN, D. A., Morven, Charlton Road, and LONG, D. P., 41, Little Heath, both in Charlton, both in London. April 8, 1930, No. 11152. [Class 40 (iv).] In a mechanical order-wire system in which an operator plugs into a junction and at once presses the order-wire key, a hunting switch for seizing the order-wire is started only if the order-wire is idle and the transmission back of the signal to key is dependent on the continuity of all the order-wire conductors a signal passed back over the orderwire extinguishing a lamp and removing a shunt from the operator's telephone so that she may hear a tone signal which is sent back over the junction. In another system the operator need not operate the order-wire key until she is informed by a flash signal over the junction that a sender is associated with a junction and with the order-wire, the flash currents when the key is pressed initiating the association of the order-wire with the key set. In both systems the sender frees itself independently of the order-wire key the completion of sending being signalled over the order-wire. Code signals over the order-wire are sent by breaking normally completed circuits in combinations. Specifications 292,331, 299,959 and 320,348, [all in Class 40 (iv), Telephones, &c.], are referred to. The Provisional Specification refers also to (a) the transmission of a signal over the junction by connecting battery to the primary of a transformer the secondary of which is connected to the junction (b) means for preventing continuous drive of the switch for associating the keys with the order-wires if there is no order-wire available, one arrangement involving two terminals in the switch for each order-wire so that the switch of a second operator moves to a waiting position and seizes the order-wire as soon as it becomes idle. First system. On the insertion of the calling plug CP, H closes a point in the chain circuit over which NU tone is given when the group is busy. The operator throws speaking key SK and order-wire key OWK of the appropriate group. If the order-wire is free, E lights SL and makes the driving circuit for OF which is stopped by T on the calling operator. T short-circuits its high resistance winding allowing TT to operate to busy the order-wire and energize LB at its incoming end. LB is followed by R, RS, LA at the incoming and A A at the outgoing end the last mentioned connecting CA in series with K which locks and connects ground to the tip of the plug shunting one winding of J on the outgoing junction circuit to cause it to operate. This method of operating J causes no appreciable click to the subscriber. J extends the talking wires so that the line relay L at the incoming end pulls up followed by LZ, AS the latter starting sender selector and junction finder when the sender selector or both switches according to which of the alternative circuits shown is employed JL connects up LC, LD which operate followed by S. At the outgoing end, AC pulls up followed by G which extinguishes SL, TS. S connects up a source of tone currents and causes the successive relapse of X .. Z. During the relapse of Y the tone is interrupted and on relapse of Z it is cut off. As shown, the tone goes out only if SZ is operated indicating that the junction has been found, but contact jz<5> is short-circuited if sending may begin before the junction is found. E which is cut off by G is sluggish enough to allow the tone signal to be received before it short-circuits the operator's telephone. The key-strip DK operates one or more of the relays CA . . CD which release the corresponding relays LA . . LD at the incoming end. These in turn transfer their setting to the register-sender (not shown). When the number has been set up, CO releases AA, AC at the outgoing end, Q pulls up and TT, T fall back. SL relights and finally TS, Q fall back. In the outgoing junction circuit C pulls up and locks on the operation of Q and connects up a reverse winding of H which however holds until the plug is withdrawn. At the incoming end, JL, S, R., RS fall and then CO, AS. PS which was operated by CO remains locked up. When the sender has completed its duty JZ, JS fall and ground is connected over bf<1> to the a-wire. I pulls up over the feed ahead, polarizes D, and energizes IR which energizes BF to disconnect the ground on the a-wire. When the called party replies D pulls up, holds itself independently of L and connects up the feed LA to give the answering signal. When the plug is withdrawn L, LZ, PS and the rest of the relays and switches at the incoming end are released. At the outgoing end H, J, C fall back. If the subscriber is busy, I, IR follow the flash impulses which are thus repeated over the junction. Premature release of the order-wire key releases all the apparatus at both ends. The junction is marked busy at the outgoing end from the incoming end by putting ground or full battery on the a-wire (an automatic battery being stronger than a manual one) e.g. by the key GK or by knife contacts operative when the selector is removed, or by a marking applied if the selector sticks off normal. C operates and connects H (ii) to the sleeve to provide the usual busy click. Second system. In this case the incoming line relay L, Fig. 9, operates to initiate the association of a register sender, as soon as the plug is inserted. LZ, AS pull up and when the sender and junction have been found JZ, JS pull up. In the incoming circuit of the order-wire JL connects battery to the receiving relays LA .. LD to seize the order-wire. LA, LC operate followed by R, RS. Interrupter FI is now connected to the a-wire to flash the supervisory lamp. The operator throws speaking key SK and presses the order-wire key OWK. SL glows, and E connects P to the a-wire. On the first operation of P, F pulls up and locks and completes the driving circuit OF. When the switch finds the depressed key, T, TT operate in series. E is thus released and SL extinguished. TT energizes TS and grounds all the order-wire conductors operating LB, LD which energize S. The operator now keys. When the number has been set up, CO energizes PS in the junction circuit and AS falls. In the order-wire circuit JL falls taking battery off the receiving relays so that R, S, RS, CO fall and at the outgoing end AA, AC are released and are followed by T, TT, TS. Lamp SL glows to indicate that the key OWK can be released. PS starts transmission by the sender. When it is completed JZ, JS fall. I pulls up over the feed ahead and polarizes D and energizes IR which energizes BF. When the subscriber replies D connects LA to the a-wire to give the answering signal. Had he been busy the signal lamp would have been flashed by I, IR. On the removal of the plug L, LZ, PS, I, D, IR and finally BF fall back the ground being connected between the relapse of LZ, BF to the junction a-wire to hold C and keep the outgoing end of the junction busy.