Patent GB-154613-A (GB)
Title: Improvements in telephone systems
IPC: H04M3/12
Filed: 1920-12-01
Abstract: 154,613. Automatic Telephone Manufacturing Co., (Assignees of Willis, B. D.). Dec. 3, 1019, [Convention date]. Automatic and semi-automatic exchange systems; time-controlling systems.-Means are provided for limiting the time during which a subscriber can have the exclusive use of a line or apparatus associated therewith. When a line or apparatus is taken into use, it is made busy, and the use thereof is made exclusive for a certain definite time, after which the subscriber is given a signal and the busy condition is removed, whereby the line is rendered accessible to other subscribers. If no other subscriber attempts to take the line, the subscriber may still continue to use it until a second subscriber extends a connexion thereto and releases the connexion of the first subscriber. In the arrangement described, a calling line of an automatic exchange is extended through the ringing selector F, Fig. 2, to an operator at the manual exchange, Fig. 3, over the two-way trunk line X, which is provided with an individual switch C<2> for establishing calls in the reverse direction. Ringing selector and connexion to manual exchange. After the calling subscriber has extended connexion in the usual manner to the ring- ing selector F, the impulses of the last digit interrupt the circuit of the line relay 9 which operates the vertical magnet 20 to raise the wipers 21, 22, 23 to the bank level in which terminate the manual exchange trunk lines. At the same time the slow-acting relay 13 closes the circuit of the stepping relay 14, which prepares a circuit through the rotary magnet 19. At the end of the vertical movement of the switch, the rotary magnet 19 is energized, and operating in conjunction with the relay 14 steps round the wipers until an idle trunk is engaged. The switching relay 16 is now actuated and, completing the circuit of the relay 17, extends the line over the trunk X at the armatures 49 and 50. Ringing-current from the generator G now operates the bridged relay 105 at the manual exchange, which relay locks itself over its lower winding and completes the circuit through the lamp L<1>. On the insertion of the answering-plug, the polarized relay 107 is bridged across the trunk conductors 101, 102, whilst the ringing-cut-off relay 15 is energized by generator current, and, locking itself over its lower winding, connects the subscriber's line to the operator over the armatures 44, 45. Timed control of busy test; release. When the operator inserts the plug in the jack J<1> the backbridge relay 8 is energized and in addition to reversing the current in the calling line in the usual manner, completes a circuit through the timecontrolling magnet 75, whereupon the roller 77, which constantly rotates in a counter-clockwise direction, begins to raise the plunger 76. After a predetermined time, for example five minutes, contacts 78 and 79 are closed and a circuit is completed through the lower winding of a relay 11, which locks itself over its upper winding, the circuit extending over the wiper 22 and the windings of the switching and stepping relays 100 and 99 of the switch C<2>. The resistance of the upper winding of relay 11 is such that while the relay 100 remains energized, the potential of the terminal 25 is sufficiently reduced to mark the trunk line idle. On the actuation of relay 11 the circuit of the magnet 75 is broken and the plunger 76 falls, and at the same time the lower winding of the relay 10 is energized, and, removing the short circuit from its upper winding, prepares at its armature 33 a circuit through the release magnet 18. In its elevated position the plunger 76 closes the springs 81, 82 and 80 and momentarily places an audible tone on the calling line to inform the subscriber that the period of exclusive use has terminated. If a second subscriber attempts to establish connexion with the trunk line X before the conversation is finished but after the period of exclusive use, connexion will be estab. lished with the trunk line in the usual manner and direct ground will be placed on the test terminal 25. Relay 11 will therefore de-energize and will complete the circuit of the release magnet 18 over armatures 38 and 36, thus restoring the selector F. At the same time, relay 17 will de-energize and disconnect the wipers 21 and 23. If the conversation is completed without interruption, the connexion is released in the usual manner. On the release of the selector F, the switch C<2> extends the trunk X to an idle first selector, the direction of current flow over the trunk being reversed and the polarized relay 107 operated to light the lamp L<2>, whereupon the operator removes the plug.