Patent GB-332956-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1929-05-01
Abstract: 332,956. Automatic Telephone Manufacturing Co., Ltd., Ostline, J. E., Taylor, R., and Beale, C. E. May 1, 1929. Semi-automatic exchange systems.-In mechanical order-wire systems in which the junction is selected by the operator, the key-set is associated with the wanted order-wire by a hunting switch or relay set in response to a momentary operation of the order-wire key. In the first of the three systems described the operator seizes the orderwire before plugging into the junction. In the others she first seizes the junction which, however, is not marked at its incoming end until she has possession of the order-wire. 1st system, Figs. 1 - - 7. The operator obtains the wanted order-wire by pressing its key 01 whereupon relay GT and magnet TM interact until TF finds the order-wire and KT, TS lock up in series, lamp FL flickering at the rate at which the operator should key. The order-wire is now marked busy in the other switches TF (the p-banks of which are not multipled) by the contacts of T'S and key 01 may be released. The operator now tests the junctions (in groups if desired) and if they are all busy throws key R to free the order-wire. When she plugs into a junction, line and release relays L, B pull up at its incoming end and GS interacts with magnet SM to drive SF to an idle register sender. At the same time SJ in the incoming order-wire circuit is energized and GJ interacts with magnet RM to drive RF to the calling junction. When the latter is reached, KK, PS lock up in series and if or when SF has found a register sender KS pulls up to seize it. BG which pulled up in series with KS entergizes TA which pulls up sluggishly and is followed sluggishly by TB, TC and is then cut off and brings down TB, TO remaining locked up. As a result, tone current from 13 is connected for two short periods to supervisory relay D which acts as a transformer. The operator then keys the number, connecting ground to one or more of the wires of the order-wire to operate corresponding relays of the storage groups MW - - MZ &c. DS operated in series with the storage relays steps on the digit distributor switch DD. When all the digits have been received, DD energizes FR which locks in series with the polarizing winding of D and brings down PS, KK, SJ, SC. In the interval between the elapse of KK, SC a circuit is made for TR, Fig. 1 which unlocks KT, TS releasing the order-wire. 2nd system, Fig. 8 (not shown) and Fig. 9. The operator first plugs into the junction and the switches RF (Fig. 9) and SF (Fig. 3) are started. She then presses the key 01 and when her keyboard is associated with the order-wire KT connects battery via the speaking key of the cord to the lower talking wire. When RF reaches the junction, JF pulls up over this circuit and energizes KK (Fig. 9) and PS (Fig. 3). This circuit can readily be modified so that RF does not start until the marking potential has been applied. In a further modification, Figs. 10 - - 12 the switch RF is omitted the junctions being associated in multiple with the order-wire. When the operator plugs into the junction, L pulls up but B waits until, as a result of her getting possession of the order-wire, battery is connected momentarily to the lower talking wire, whereupon it locks up under control of L. This impulse is given with the aid of a relay ST energized by the order-wire key and falling sluggishly when KT pulls up. On the operatioen of B, PS, KK pull up in series and SF hunts for a sender. When all the digits have been registered, FR pulls up, disconnects the order-wire from the junction circuit and brings down KK, SC whereupon an impulse is sent as in the other systems to free the outgoing end of the order-wire. Transmission by and release of register sender. SS, energized over DD2 when the 1st digit has been received sends back a momentary tone signal with the help of TA and energizes CC when next springs 23 open to connect them to magnet SDM of sending switch SS and initiate transmission in known manner under control of pickup and stop relays SA, SZ and sender control switch CS. SZ has a locking circuit via C3, DD2 to hold up transmission if the next digit has not been keyed. When all the digits have been sent, CO bridges the trunk and cuts off BG which unlocks all the relays and homes the switches. Offnormal relay BP holds CO until all the switches are home. Supervision of call. KS falls back on the energization of CO cutting off battery over LA from the lower talking wire. When the called party replies D connects it up again. If a busy-flash is encountered the impulses are repeated back by I. Cancelling wrong setting.-The operator withdraws the plug and re-inserts it. KS, BG fall back and SF hunts for a new sender being unable to re-seize the original one because the test circuit is held open by BX which holds for a short time after the relapse of BG.