Patent GB-150727-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1920-05-11
Abstract: 150,727. Western Electric Co., (Assignees of Polinkowsky, L.). Sept. 10, 1919, [Convention date]. Addition to 144,264. Automatic and semi-automatic exchange systems.-In setting up a call from a subscriber belonging to an exchange equipped with powerdriven selectors to a subscriber belonging to an exchange equipped with step-by-step selectors, the selectors at both exchanges are controlled by a register-controller at the first exchange. When connexion has been made by a selector at the first exchange to an inter-exchange trunk 151, 152, a switch 300, Fig. 1, associated with the out-going end of the trunk, runs through a complete cycle for each of the remaining digits, intermittently opening the trunk circuit at contact 303, so as to forward impulses over the trunk to the step-bystep selectors at the distant exchange, Fig. 2, and intermittently closing a contact 302 to advance one of the registers of the register-controller, which is shown at the bottom left-hand corner of Fig. 1. When the register regains its normal position it de-energizes a relay 121<1>, short-circuiting the contact 303 so as to prevent the transmission of any more impulses during the remainder of the cycle of the switch 300. The switch 300 thus acts as an impulse-transmitter, forwarding sets of impulses corresponding to the complements of the positions to which the registers have been set. Operation of the switch 300 as an impulse-transmitter. A power-driven group selector extends the calling line to an idle inter-exchange trunk in known manner, and the associated sequenceswitch, moving to its 6th position energizes the stepping-relay 116 of the register-controller 150 in series with relay 121<1>. A sequence switch 130 is now driven to its 2nd position, bridging the outgoing trunk through contacts 143. 303, and closing a circuit through contact 131 to start switch 300 on its first cycle. Contact 303 is now intermittently opened to produce current-interruptions in the trunk circuit, and contact 302 is intermittently closed to ground a point in the circuit between relays 121', 116, short-circuiting the latter, which advances a register from its set position towards its normal position in known manner. When the register reaches its normal position the circuit of relays 116, 121<1> is opened by relay 115, and relay 121<1> de-energizes, driving switch 130 to its 3rd position and short-circuiting contact 303, so that for the remainder of the cycle of switch 300 the trunk circuit remains closed. During this period the group selector at the second exchange, which has been set by the impulses generated at contact 303, performs its hunting operation to find an idle connector of the selected group. When switch 300 regains its normal position a circuit 301, 132 is closed to drive switch 130 to its 4th position. Relays 116, 121<1> are again energized in series, and switch 300 is started on its second cycle, which proceeds as before, and later, in the 6th position of switch 130, switch 300 runs through its third cycle. In these two cycles it generates impulses for controlling the connector at the second exchange, the numbers of impulses transmitted in the different cycles being controlled by different registers of the register-controller. Operation of the group selector 230 and connector 240, Fig. 2. The first series of impulses are repeated by relay 201 in the usual way to the primary stepping magnet 204. and a slow-release relay 203 then relapses and completes the circuit of the secondary stepping magnet 205, which is de-energized a moment later by the relapse of relay 206, which was energized by relay 203. The selector is thus moved to the first set of terminals in the selected level. If these are busy, relay 206 is energized again over the test wiper 210 and off-normal contact 229 and again energizes magnet 205, which steps the wipers to the next set of terminals and open-circuits relay 206, and the alternate energizations of relay 206 and magnet 205 continue until the terminals of an idle connector are reached, whereupon relay 228 becomes energized (being no longer short-circuited over a grounded test circuit) and locks itself to the test circuit, which is now grounded by the energization of relays 214, 215. The next series of impulses are repeated by relay 214 to the primary stepping magnet 217 of the connector, and the relapse of the slow-release relay 216 then deenergizes magnet 219 to trip the side-switch to its 2nd position. The final series of impulses are repeated to the secondary stepping magnet 218, and relay 216 then again relapses. Busy test and signal. If the wanted line is busy, the energization of magnet 219 is continued, after the relapse of relay 216, by a circuit through relay 223 and the grounded test terminal 235. Relay 223 locks this circuit, so that the side-switch is held in its 2nd position and a busy tone coil B<2> is connected to line. Supply of ringing current. If, however, the wanted line is idle, the relapse of relay 216 is followed by the de-energization of magnet 219, and the side-switch is tripped to its 3rd position, energizing relay 226, which connects the line to a source of ringing current and to relay 225. In the meantime, after the transmission of the impulses of the final digit, switch 130, Fig. 1, has been driven from its 6th to its 10th position, transiently closing at contact 135 a circuit for relay 121', which locks itself up in series with relay 120. Relay 122' is now bridged across the trunk 151, 152 in series with relay 214, but a resistance 238 included in this circuit in the 3rd position of the side-switch prevents relay 122<1> from responding, so that a circuit 140, 139 is closed to drive switch 130 to its 13th position. Relay 104, which was energized over contact 136, relapses and may operate a signal to indicate that ringing-current is being supplied. When the called subscriber answers, relay 225 is energized and locks itself up, connecting the called line to the feed relay 224, which short-circuits resistance 238 so as to energize relay 122<1>, which drives switch 130 to its 14th position, and conversation proceeds. Relay 104 is now energized in circuit with impedance 146 and contacts 140, 138. Release. When the called subscriber disconnects himself, the de-energization of relay 224 removes the short-circuit from resistance 238, deenergizing relay 122<1>, which de-energizes relay 104, which may actuate a signal before the operator, if the system is a semi-automatic one, or may directly initiate the release of the power-driven selector, if the system is full-automatic. The restoration of the selector de-energizes relay 121', which drives switch 130 to normal, opening the trunk circuit 151, 152 so as to release the selectors at the second exchange in the usual manner.