Patent GB-774034-A (GB)
Title: Improvements in or relating to allotting arrangements
Inventor: JACKSON RAYMOND ARTHUR
IPC: H04Q3/00
Filed: 1955-03-12
Abstract: 774,034. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. Dec. 13, 1955 [March 12, 1955], No. 7304/55. Class 40 (4). An arrangement for allotting for use one of a number of equipments comprises two relay chains each operating cyclically, one relay chain passing through a number of cycles to cause the other chain to pass through one cycle, the two relay chains controlling contacts which test in cyclic order for the first idle equipment. In Fig. 2, leads 10 to 25 extend from group selectors to the allotter shown, and each group selector when idle puts resistance battery on its respective lead and on a lead BL common to all selectors to actuate or hold a relay AGB. Relays A, B, C and D, interact cyclically so long as contact agb is made and the test relay T is not energized. When contact agb makes, relay A is actuated over the left-hand winding and energizes the left-hand winding of B in series with its own right-hand winding. When actuated B disconnects the left-hand winding of A and shortcircuits the right-hand winding of A so that A falls back slowly. On relapse of A relay C is energized over its left-hand winding in series with the right-hand winding of B and when C is actuated the left-hand winding of B is disconnected and the right-hand winding is shortcircuited to cause B to fall back slowly. On relapse of B relay D is energized and causes C to fall back slowly and when this relapses A is energized to cause the slow release of D. When D falls back B is energized to release A as at the beginning of the cycle. During a full cycle of the allotter, relay A makes and breaks a contact in a second relay chain AA, BB, CC, DD, four times. When A first pulls back AA operates over its left-hand winding and when A first relapses BB pulls up with its left-hand winding energized in series with the righthand winding of AA. On the second actuation of A relay AA is released while BB holds and when A relapses again CC is operated in a circuit which holds BB over its left-hand winding. When actuated for a third time A onuses the release of BB while holding CC, and when A is released for the third time DD is pulled back in series with the right-hand winding of CC which holds. On the fourth energization of A relay CC falls back while DD holds until A releases for the fourth time when DD falls back and the second relay chain rests until A operates again. Each combination of relays made during the time one of the relays A, B, C or D is releasing makes a connection from one of the leads 10-25 to the test relay T. When a lead marked idle by battery is tested, relay T responds over both low resistance left-hand and high resistance right-hand windings and at contact t removes the short circuit from whichever relay is releasing so that the allotter is halted and maintains the connection to the marked lead pending a call. When a call is initiated earth is put on a common lead S from the subscriber's line circuits and a relay HS responds to short circuit the high resistance winding of relay T over contacts t and agb. The increase in current over the marked lead is detected by undisclosed means within the group selector to actuate a line finder and when the group selector is connected to the calling subscriber's line circuit earth is taken from lead S to release HS, and idle marking is removed to release the test relay and enable the allotter to hunt for and pre-allocate the next idle selector. If no other group selector is idle AGB will release when the last selector is taken into use so that contact agb halts the allotter on the lead last tested, or on a subsequent one, depending on whether T releases after or before AGB. In the event of a line finder failing to operate it is stated that a timed step on facility may be introduced into the allotter circuit so that it is not permanently halted.