Patent GB-343522-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1929-11-20
Abstract: 343,522. Automatic exchange systems. AUTOMATIC TELEPHONE MANUFACTURING CO., Ltd., Strowger Works, and TAYLOR, R., 30, Oulton Road, Wavertree, both in Liverpool. Nov. 20, 1929, No. 35527. [Class 40 (iv).] In a mechanical order wire system, when a junction incoming at an automatic from a manual exchange is seized, a hunting switch at the automatic exchange is set in operation to connect up the control line extending from the originating exchange, whilst at the originating exchange the operation at the " A " operator's position of the hunting switch which connects her key set with the control line is dependent on the operation of the speaking key associated with the cord over which the connection is to be set up. Specifications 315,735 and 332,956, [both in Class 40 (iv), Telephones &c.], are referred to. General operation. A free junction OG5 is selected seizing a junction relay set JRS at the automatic exchange. The relative order wire key ow is then operated and the speaking key SPK thrown. The keying trunk finder switch KTF hunts for the circuit marked by ow whilst at the automatic exchange GKF hunts for the incoming end of the keying trunk. A sender is seized over OPS which finds the junction to be used over JFS. When the sender is ready visual and audible signals are given to the operator who keys up the number, the trunk being freed for further use immediately the sender has been set. Connection of sender to keying trunk. A plug is inserted in a jack JJ, Fig. 1, connected with a free junction to the required exchange. Relays S and T at the manual exchange pull up and relay L at the automatic exchange (Fig. 3) energizes over conductor 10. The operator depresses the order wire key OW, which must be held down during the whole of the selecting operation, energizing relay ST and if the speaking key SPK has been operated, or if not when it is operated, SR pulls up allowing high resistance relay GT to energize in series with KT. Relay GT and magnet KTM interact stepping KTF until the circuit marked bv OW is reached when KT and TS energize in series stopping hunting and extending the key-set to the mechanical order wire. ST releases, but during its slow period battery is connected to conductor 13 to energize relay LZ [kt1, st3, SPK, tip of plug (not shown), 13]. LZ completes a circuit for AS and GC in series, and another over 15 and 20 for JO. JO energizes connecting flicker earth to lamp SLP and breaking the circuit of clear down relay FR. This latter relay is made sufficiently slow to operate to allow JO to be energized on a normal call before FR pulls up. Relay GC prepares a circuit for G to energize in series with K and marks the selected control trunk in the bank of GKF. Relay G and magnet GKM interact until the selected circuit is reached when K energizes stopping the switch and connecting earth through its very low resistance upper winding to mark the contact as busy. Relay K also completes a holding circuit for JO in series with ZF (Fig. 5) at armature k2 completes a circuit over conductor 22 for initiating the operation of the associated sender finder and junction finder switches and at k4 prepares a circuit for AS and TD in series. If more than one AS relay is connected to the circuit TD pulls up energizing PR to release the connection as described later. If, however, only one AS relay is connected this relay energizes, and not TD, marking the selected junction relay set JRS in the banks of the finder switch JFS. When JFS has connected to JRS relay JS pulls up connecting the impulsing leads from the sender to the automatic switches and energizing PS. When a free sender is found SP (Fig. 4) energizes by way of kk and py in the sender, extending the keying trunk to the sender, connecting a tone over conductor 25 and completing a circuit for the relays, TA, TB, TC, which interact to connect two short tone periods to conductor 13 to inform the operator that a sender is waiting. Moreover, when the sender is seized battery is connected over wipers 6c and 27, 28 to energize SK, which relay locks up, connects conductors 20, 28 to the keyset and replaces the flickering condition of lamp SLP by a steady glow. Either the visual or the audible signal may be omitted. Release of keying trunk. The number is keyedup in the usual way and when completed PY (not shown) in the sender energizes opening contact py to release SP. SP opens the circuit of PR and during the slow release period of this relay a circuit is completed for TR which operates to release SK, TS and KT, freeing the keying trunk. Relay PY also steps OPS to preselect a free sender and the sender remains in use until the number has been pulsed out when JS de-energizes connecting the calling and called circuits. Relay I operates and IR pulls up energizing BF. When the called subscriber replies D energizes connecting retard LA to conductor 13 to provide answering supervision. Called line busy: release. If the called line is busy, busy flash consisting of intermittent application of battery potential to both speaking conductois is received. Relay D does not energize but I relapses at each application bringing down IR which at ir1 repeats the flash to the operator. A distinctive tone is also connected to the circuit. The operator withdraws the plug from JJ to release the circuit. If the operator clears during a battery period LZ, which is held from battery on the lower conductor, holds PS energized to guard the junction until the conclusion of the period. If the battery period is again applied after LZ has released, but before PS has fallen away, LZ reoperates (ps8, ir2, ps7) guarding the trunk until the termination of the flash. Relay T guards the junction against seizure during the period after removal of the plug and before JRS has released. Emergency features. In the event of the keying trunk proving faulty it may be replaced by the last two junctions of the group. In addition one emergency group keying trunk finder GKF and associated relays may be brought into operation by a relav not shown. Time pulse release features are provided in the sender for releasing the trunk in cases of delay and cancellation of a number is effected by operation of the key CK.