Patent GB-663973-A (GB)
Title: Improvements relating to the step-wise control of a motor-driven uniselector of the kind used in telephone and like selective systems
IPC: H01H67/06
Filed: 1949-06-23
Abstract: 663,973. Automatic exchange switches. SIEMENS BROS. & CO., Ltd., and LONG, D. P. June 23, 1950 [June 23, 1949], No. 16725/49. Class 40 (iv). A motor-driven uniselector of the type described in Specification 388,173 is caused to operate step-by-step by the provision of circuit arrangements in which a high-speed relay is operated by the connection of its low resistance operating winding between the two camoperated contacts connected to the field coils of the motor and connects a high resistance holding winding across the cam contacts, a step being initiated by opening the operating circuit and terminated by the release of the relay by short-circuit when both cam contacts are closed at the same time during the step. The switch is stopped either by the energization of both field coils or by de-energization of both coils and release of the latch magnet. Switch stopped by energization of both coils, Fig. 1. In the normal condition a low resistance bridge is completed over back contacts of impulse relay A and control relay X between the cam-operated contacts m1, m2 connected to the field coils M1, M2 respectively. Assuming m1 to be closed the reception of an impulse brings up A followed by C and latch magnet LM connects ground to M1 directly and to M2 via winding (I) of X. Both field coils are energized substantially equally and the armature does not move. At the end of the impulse A releases and opens the circuit of winding (I) of X but high resistance winding (II) remains in, series with coil M2 and the consequent reduction of flux due to that coil results in the rotation of the armature under the influence of M1. After nearly a quarter revolution m2 closes before m1 opens and winding (II) of X is short-circuited. X releases either by the time m1 opens or shortly after, due to current reversal in winding (II). Both M1 and M2 are then energized and the armature stops, the wipers having made one step. Further impulses result in a step-bystep advance of the wipers. At the end of the train C falls away and releases LM which disconnects the driving ground and re-engages the latch to lock the wipers. Switch stopped by de-energization of both coils. The embodiment of Fig. 2 (not shown) which is particularly useful for slow stepping dispenses with the bridge over back contacts of X and A, and the latch magnet is under direct control of these two relays. Operation is similar to that of Fig. 1 except that A and X release during each step and LM follows, disconnecting the driving ground and engaging the latch at the end of each step. Fig. 3 shows arrangements for an allotter which is required to take one step when taken into use to ensure that it will not seize the same circuit for two successive calls. The contacts of test wiper P are connected to battery in free line finders, T is the test relay and SM the control relay. When the allotter is taken into use the starting relay ST (not shown) operates and brings up LM which energizes both M1 and M2. Relay X pulls up over winding (I) and short-circuits T. Slow-to-operate SM then comes up and disconnects winding (I) of X to rotate the armature. X is then released as before and if the line finder on to contacts of which the allotter has stepped is free T operates over both windings in series. LM is released and the high resistance left-hand winding of T is shortcircuited to busy the line finder. If the line finder is found busy T remains down. With SM up X is disconnected and the motor continues to run under control of cam contacts m1 and m2, as described in Specification 388,173 until T operates to a free line finder.