Patent GB-353989-A (GB)
Title: Improvements relating to automatic and semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1930-05-30
Abstract: 353,989. Automatic exchange systems SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and HUMPHRIES, H. E., 47A, Lewisham Hill, both in London May 30, 1930, No. 16761. [Class 40 (iv).] In a system employing register-controllers of the code translating type, if the first or a subsequent code selector fails to find an idle junction in the required direction, a low-frequency alternating current (e.g. ringing current) signal is sent back to the register-controller, which effects release of the partial connection and controls the setting up of a fresh connection over an alternative route. The alternative routing number is sent under control of an auxiliary single-motion switch which sets itself in accordance with the setting of the BC switch. First code selector, Fig. 2. Line and release relays L, B energize and connect up impulse relay A in series with relay I and shunt-field relay D. Relay C energizes and connects up relay MG, which acts as a stepping relay for the switch AD. When an idle A digit switch is found, relay K operates and connects release relay B to wiper PU and impulse relay A to the + and - wipers. The dialled digits are repeated at contact l2 to operate the A digit switch and the registering switches in the register-controller. The first impulse train sent out from the register-controller is repeated by relay A to the vertical magnet V, release relay BA energizing at the first step, and change-over relay C then falls back and connects up rotary magnet R which interacts with stepping relay G, test relays HA, HB being connected to test wipers P1, P2 and the arrangement being such that the upper set of wipers has preference if both engage idle outlets. Relay A is disconnected when one of relays HA, HB operates and succeeding impulse trains are sent directly over the line wipers. The register-controller and A digit switch release, and the switch AD restores, release relay B being held locally after relay K falls back. Upon reply of the called party, shunt-field relay D operates and metering is effected after an interval by means of relays DA, DB under control of pulses over wires SP, ZP. Release takes place in the usual manner. If a forced release condition arises relay M energizes over wiper FR, short-circuiting relay K to release the A digit switch and lighting lamp bl. Subsequent dialling operates the vertical magnet V through relay A and NU tone is connected up. Register-controller, Fig. 3. Upon seizure by an A digit switch, relays A, B, BA energize, and the second and succeeding dialled digits are repeated at contact a1 to the magnets BCV, BCR of the BC switch and the magnets TH, HU, T, U of the number registering switches, the units registering switch U advancing one step after each digit under control of series relay CA to direct each train of impulses to the appropriate magnet over wiper u4. The routing number is determined by the jumpering between the banks of the BC switch and terminals 1-10 and DCO. As soon as wiper u2 reaches position 3, relay IG energizes and closes a circuit over impulse springs IM2 for magnet S of the sending switch, which in position 3 places the outgoing loop under control of impulse springs 1M1. When the requisite number of impulses have been sent, a circuit is closed over u2, c2, bc1, s4 for relay SZ, which short-circuits impulse springs IM1 and steps the sending switch to normal. The control switch C advances one step. Assuming for example that the routing number comprises a single digit only, a self-interrupting circuit is now completed for the switch C over terminal DCO and wiper c5 and is maintained by relay J until position 13 is reached, whereupon the numerical digits are transmitted under control of wipers th2, hu3, t3, u5. The control switch then moves into position 17, in which relay CO energizes and initiates release of the register-controller and A digit switch. Forced release if the register-controller is held for more than a given time is effected by relays TP, M under control of pulses over wires SP, ZP. Spare positions of the BC switch are jumpered to terminal SC, and if the switch is set to such a position, relay M effects forced release. Alternative routing. If the first code selector fails to find an idle junction in the selected level, test relay HA operates in the eleventh position and connects A.C. through the left-hand secondary winding of a transformer T, Fig. 1, to the impulsing loop. A similar circuit may be effective at a subsequent code selector on certain levels on which post springs NP1, Fig. 1, are operative over the right-hand winding of a transformer T and line relay A. In either case shunt-field relay D, Fig. 3, responds intermittently, connecting up sluggish relay DD over wiper c3 and advancing the auxiliary switch ED to position 3, in which relay EG pulls up, opening the impulsing loop and connecting ground over relay JRA to wiper JR of the switch AD, Fig. 2, to the release magnet Z of the first code selector, which restores to normal, but relays L, K, B, A remain operated. If the congestion occurs at a subsequent code selector, the partial connection is released by the disconnection of relay HA or HB. The control switch C advances automatically to position 6 owing to the operation of relay EG, whereupon a fresh circuit is closed for stepping the switch ED to a position determined. bv cross connections between banks ed8 and bc6. Relay ET then pulls up, locks, disconnects relay EG, and advances the switch C to position 7, in which a circuit is closed for relay IG to restart impulse transmission as already described, an alternative routing number being sent under control of banks ed2-7 of the switch ED, which are jumpered to terminals 1-10 and DCO. Calls to manual boards. Shunt-field relay D energizes due to the wires from the O level of the A digit switch being crossed and connects up relay MB which at once initiates transmission of a routing number determined by the jumpering between its contacts and terminals 1-10 and COT.