Patent GB-183939-A (GB)
Abstract: 183,939. Western Electric Co., Ltd., and Polinkowsky, L. May 4, 1921. Automatic exchange systems. - A selector, acting as a repeater for reverting impulses from a succeeding selector, is so controlled that it is not placed in a condition to repeat the impulses until the fundamental circuit is completed at the succeeding selector, this being secured by arranging that a sequence switch controlling the selector repeater remains in a waiting position until a relay bridged across the outgoing trunk becomes energized. The invention is described with reference to a system in which a connection is established by a third group selector A, Fig. 1, over a two-wire trunk 45, 46 to a fourth group selector B, Fig. 2, and thence to a final selector (not shown), part of the system described being identical with that described in Specification 184,249. When the selector A has seized an idle trunk 45, 46, the test relay 40 breaks the circuit of the line relay 3 to stop the brushes and to drive the sequence switch 20 to its 5th position. Relay 3 energizes over the incoming fundamental circuit to drive the switch 20 to its 7th position in which a relay 9 is bridged across the outgoing trunk in a circuit 53, 12, 9, 11 and back contacts of relays 6, 52. Relay 9 energizes in series with the line relay 100 at the selector B which energizes relays 104, 109 in a circuit 105, 107, 104, 108, 109, 110. Relay 104 drives the sequence switch 111 into its 2nd position in which the trip-spindle magnet 116 is energized. The intermittent grounding of the fundamental circuit 45, 46 at the spring 121 short-circuits the bridged relay 9 which repeats the impulses to the register-controller by earthing the fundamental circuit 1, 2 over contacts 30, 28, 23, 4, 5, 25. The opening of the fundamental circuit 1, 2 at the registercontroller after the required number of impulses has been sent back, de-energizes relay 3 to drive the switch 20 to its 8th position in which the bridged relay 9 is replaced by a high-resistance relay 15 in a circuit 53, 55, 15, 56. The breaking of the bridge circuit when the switch 20 moves from its 7th position de-energizes relay 100 to drive the switch 111 to its 3rd position in which relay 100 energizes in a local circuit 101, 114, 141 and off-normal springs 120, 119, and closes the circuit of the brush-carriage magnet 132 which rotates the tripped set of brushes to hunt for an idle trunk to the final selector. Upon the seizure of an idle trunk, the test relay 104 operates, de-energizing relay 100 to drive the switch 111 into its 5th position in which the fundamental circuit 45, 46 is extended directly over the resistance 102 and the brushes 133, 134 to the final selector, and the high-resistance relay 15 energizes in series with the line relay at the final selector which, however, does not yet energize. In the 8th position of the switch 20, the relay 3 cannot energize over the fundamental circuit 1, 2 until earth is placed upon the upper conductor 1 by the relay 15, and the switch 20 waits, therefore, in its 8th position until the completion of the fundamental circuit extending to the final selector as just described. Relay 3 now energizes to drive the switch 20 into its 10th position in which the relay 9 is again bridged across the line and the selector A is in a position to repeat the tens impulses sent back from the final selector. The line relay at the final selector energizes over the fundamental circuit in series with the bridged relay 9 to move its controlling sequence switch into its 2nd position in which the trip spindle is rotated, sending back impulses which are repeated to the register controller by the relay 9 over the circuit previously traced. At the end of the tens impulses, the opening of the fundamental circuit 1, 2 at the register controller de-energizes relay 3 to move the switch 20 into its 11th position in which the relay 15 is again bridged across the trunk 45, 46, the disconnection of the relay 9 causing the sequence switch of the final selector to move into its 3rd position in which the fundamental circuit is completed by the usual batterv and earth connections. The switch 20 waits in its 11th position until this connection is completed, whereupon the relay 15 energizes to move the switch 20 into its 13th position in which the relay 9 is once more bridged across the line and repeats the units impulses sent back from the final selector in. the same manner as described above for the tens impulses. Specification 176,911 also is referred to.