Patent GB-186037-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1922-07-20
Abstract: 186,037. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Wicks, J.). Sept. 10, 1921, [Convention date]. Automatic exchange systems.-Relates to improved circuit arrangements for selectors and rotary connectors having two sets of wipers for testing two lines simultaneously. Description is given of the extension of a call through a selector D and connector H both having additional bank contacts and associated wipers, to a private exchange, which may have more than ten trunk lines X, Y to the main exchange, the connector being controlled in its rotary movement, first by number impulses and then by circuits from the test wipers. Selector D. If the first trunk engaged by the first set of wipers 70-72 is busy, a circuit is completed at the earthed test contact for a wiper switching relay 38, which brings the second set of wipers 73-75 into operation. If the trunk engaged by these wipers is also busy, the stepping relay 36 is energized by the earthed test contact to rotate the wipers a further step, and so on until the wipers 70-72 say, engage the contacts 78-80 of an idle trunk line. The switching relay 38 is then de-energized, and a previously short-circuited switching relay 37 is energized in series with the stepping relay 36. Should the wipers 73-75 be the first to engage the contacts of an idle trunk line, the switching relay 38 is maintained energized at the armature 58 of the relay 37, keeping the connections transferred to the wipers 73-75. If all the trunk lines are busy, on the last step of the wipers, cam springs 41, 42 are operated to give a busy tone to the calling subscriber. Connector H. A slow relay 109 energized in series with the rotary magnet 114 during the passage of the last set of impulses, completes the circuit of a slow relay 111, which connects the test wiper 165 of the first set to the test relay 108, and energizes a slow relay 110, preparing at the armature 147 a point in the testing circuit of the test wiper 171 of the second set. If the first trunk is busy, the test relay 108 energizes, locking itself, and at the armature 138 connecting the second test wiper 171 to the stepping relay 107, which if the second trunk also is busy operates the rotary magnet 114 and the slow relay 111 in parallel, and rotation is repeated until an idle trunk line is found. If the first set of wipers engage an idle trunk, the test relay 108 and slow relay 111 de-energize, completing a circuit from the grounded test conductor 91 through the lower winding of a switching relay 112 to the switching relay 180 and motor magnet 181 of the P.B.X. line switch C'. If the second set of wipers engage an idle trunk, upon release of the slow relays 111, 110, a circuit is completed through the switching relay and motor magnet of the P.B.X. line switch, and the lower winding of a switching relay 113, which closes the circuit of the switching relay 112 and the call is extended as before except that the switching relay 113 transfers the connections to the second set of wipers and the associated trunk line. Busy signal. If there are an odd number of trunk lines, the second of the last two sets of contacts will be dead. On engagement of the wipers with these sets, the test relay 108 remains energized, and upon release of the slow relay 110, a busy signal is sent to the calling subscriber. If there are an even number of trunk lines, earth is permanently connected to the test contact of the first set of the first pair of dead sets of contacts. If the trunk lines occupy a whole level in the connector, in the eleventh rotary position of the wiper shaft a cam 124 operates a spring 123, connecting the busy machine to the line relay 101. Release. When the calling subscriber replaces his receiver the line relay 101 is released, and an impulse is sent through the slow relays 109, 111, only the latter of which energizes, removing earth from the test conductor 91 at the armature 150, and energizing relay 110, which, when the switching relay 113 is in operation, removes earth from the test conductor 91 at the armature 147. Deenergization of the slow relay 102 releases relay 111 at the armature 127, and removes earth from the test conductor 91 at the armature 126, releasing the selector D and line switch C. Release of relay 111 opens the circuit of relay 110, and again connects earth to the test conductor 91 through the switching relay 112 to prevent seizure of the connector H by another selector at this stage. When the called subscriber replaces his receiver, the back bridge relay 100 de-energizes, releasing the ring cut-off relay 105 and the switching relay 112 at the armature 197, and energizing the release magnet 106 at the armature 196.