Patent GB-864637-A (GB)
Title: Improvements relating to selector systems
Inventor: WARMAN BLOOMFIELD JAMES
IPC: H04Q3/42
Filed: 1958-08-15
Abstract: 864,637. Automatic exchange systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Aug. 4, 1959 [Aug. 15, 1958], No. 26345/58. Class 40 (4). In a multi-stage selector system having different " free " test terminal potentials for the successive stages, a single testing circuit controls outlet selection in all the stages, having associated therewith in respect of each stage a switching circuit when, when a particular outlet or group of outlets in the relevant stage is reached by a selector under control, is operable to apply to a potential responsive device of the testing circuit a reference potential which, having a different value for each stage, ensures that the device responds on receipt from the selector of the relevant " free " test terminal potential but not on that of a " free " test terminal potential relevant to any subsequent stage, the device on so responding being effective to stop the selector. In the arrangement described the selectors are assumed to be high-speed motordriven uniselectors which revert impulses to the controlling registers via their (C) arcs. Operation of first selector W.-Ground is extended from the register over a registercoupling connection RL2 initially via the (+) wiper and home contact and subsequently via the operated latch contact lc to the selector latch magnet LM whereupon the selector is driven until the number of impulses reverted from the (C) arc over connection RL3 indicates that the wanted group has been reached. During this time the (P) wiper is connected over RL1 to the base of Tr1in the testing circuit TC, but with Tr4 non-conductive the - 40 V. connected to the emitter of Tr1 does not permit Tr1 to conduct to the " free " potential of- 40 V. encountered by the (P) wiper. When the wanted group is reached, however, the register applies a stimulus over lead l5 to the bi-stable switching circuit TP1 which responds and applies to lead l1 a potential which allows Tr4 to conduct. The reference potential thus produced at its collector is applied to the emitter of Tr1 which is then rendered conductive by the " free " (- 40 V.) potential of a free second group selector X appearing at the relevant (P) arc outlet of the first group selector W. The test relay TA pulls up, thus opening the latch magnet circuit. Restoration of the latch contacts lC of group selector W extends the latch magnet energizing circuit via the (+) arc to the latch magnet LM of the second group selector X. In the register the test relay TA holds in a temporary holding circuit and brings up the switching relay WT, which restores the switching circuit TP1 to normal (whereupon Tr4 and Tr1 cease to conduct), and completes a circuit for the slowoperating switching relay WA. The operation of WA releases WT and breaks the holding circuit of TA, WT in turn releasing WA, which reestablishes the latch magnet circuit over RL2, this time to energize the magnet LM of the second group selector X. All first selector outlets in required group busy.- In this event, when the selector W reaches the end of the group the impulse reverted from the (C) arc resets the switching circuit TP1, whereupon Tr4 and Tr1 become non-conductive. The selector is driven on to the penultimate outlet at which the (P) wiper encounters the " busy " potential of- 50 V. to which Tr7 and Tr1 conduct. Busy relay GB stops the selector, connects up busy tone, and prevents relay TA from operating WT. The selector remains on its penultimate outlet until it is homed. Operation of second group selector X.-A distributer, part of which is represented by the multi-position switch D, is stepped after the setting of each selector, so that after the first selector has been set the relay SB is operated. This connects up Tr5 instead of Tr4, and changes the collector potential of Tr1, Tr2 and Tr3, the emitter potential of Tr2 and Tr3, and the potential connected to the base of Tr7 and Tr1. When the selector X reaches the wanted group the register operates TP2 whereupon Tr5 conducts and Tr1 can then respond to the " free " (- 30 V.) potential of a free final selector. Operation is then similar to that of the first group selector W. Setting of final selector Y to an ordinary outlet.-In the final selector an impulse is reverted from the (C) arc at every outlet and when the selector reaches the outlet immediately preceding the wanted one the register applies a stimulus over lead l9 to the switching circuit FT which thereupon primes the AND gates G2 and G3. The next impulse reverted (that from the wanted outlet) passes via lead l13 and gate G2 to operate the switching circuit TP3. Prior to the commencement of the final selector setting action the distributer D has stepped on and brought up relay SD so that the emitter of Tr1 is now connected to the collector of Tr6. Operation of TP3 renders Tr6 conductive, thus connecting up to Tr1 the reference potential for the final selector stage. If the wanted outlet is free, Tr1 conducts, TA operates and the selector is stopped. The pulse reverted from the wanted outlet also restores FT to normal (but not before TP3 has had a chance to operate) whereupon the AND gates G4 and G5 are primed. If the wanted outlet is not free, so that the final selector is not stopped at it, the next impulse reverted passes via gate G4 to restore TP3 to normal, whereupon Tr6 and Tc1 become non-conductive. The selector drives to the penultimate outlet where it is stopped by the busy relay GB as before. Setting of final selector Y to a P.B.X. group outlet.-The impulse reverted from the first outlet of a P.B.X. group is derived from ground via Rs13 instead of from a - 10 V. or - 20 V. source as for ordinary lines. Consequently this pulse is not only applied to G2 to operate TP3 but also by way of gate GE to prime G3 and G5. Gate G3 passes the output of FT to operate TP4 independently of TP3. With the intermediate outlets of a P.B.X. group reverting " ordinary line " impulses and the last outlet of a P.B.X. group reverting a ground impulse the switching circuit TP4 maintains the reference potential on the emitter of Tr1 until, if all the P.B.X. lines are busy, the impulse from the last outlet passes via G5 to restore TP4.