Patent GB-161950-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/62
Filed: 1921-04-11
Abstract: 161,950. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Lomax, C. E.). April 19, 1920, [Convention date]. Automatic and semi-automatic exchange systems.-Incoming calls from a manual main exchange to an automatic private branch exchange can be set up by an operator at either exchange, and outgoing calls are conveyed by the same group of trunks, an idle trunk being taken into use either by the P.B.X. operator or by a connector controlled by a P.B.X. subscriber. The 'varying conditions of a trunk and of the connector associated with it are indicated to the P.B.X. operator by lamp signals. Incoming calls; operation of the connector H, Fig. 3, by the main exchange operator. When the operator plugs into the jack J<1> of the trunk 30, 31 the sleeve relay 12 is energized and closes a circuit over the wire 31 for relay 13 and the connector line relay 101, which energizes the slow-release relay 102, which grounds the busy wire 95. The operator brings her impulse-sender S into the circuit 31 by key K<1>. The first set of impulses are repeated through slow-release relay 104 to vertical magnet 109 in a circuit 116, 125, 132, 119 and at their conclusion relay 104 relapses and closes a circuit through off-normal contact 163 for slow-release relay 103, which locks itself so as to remain energized whether relay 104 is energized or net. At the first vertical step the original circuit of relay 102 was opened by contact 163, but as long as impulses were passing, this relay was kept energized by relay 104. The relapse of relay 104 is followed by that of relay 102, ground being now applied to the busy wire 95 by relay 103. The second set of impulses are repeated through relay 104 and contact 122 to rotary magnet 110, relay 104 being again energized and energizing relay 102. Busy release and signal. When the relay 104 relapses at the termination of the second set of impulses, and before relay 102 has had time to de-energize, release magnet 112 is connected through off-nornial contact 164, the lower winding of relay 105 and contacts 118. 123 to the test wiper 141, so that if the wanted line is busy the connector is at once released, and relay 105, locking itself through its upper winding, connects a busy tone machine Q to the calling trunk. Supply of ringing current. If the wanted line is idle, the relapse of relay 102 closes a circuit through relay 108 in series with the cut-off relay 146. Relay 108 grounds the test wiper, locks itself up in series with magnet 110, and completes a circuit from the ringing-generator P over the selected line. When the called subscriber answers, a ringing cut-off relay 107 is energized and locks itself up, completing the speaking circuits and energizing a back-bridge relay 106, which locks the relay 101 and disconnects it from the lower trunk wire. Main exchange operator's supervisory signals; release of connector. The disconnection of relay 101 from the lower trunk wire, when the called subscriber answers, causes the de-energization of relay 13, Fig. 1, which completes a metallic bridge through the left-hand windings of the repeater R, energizing relay 5, which short-circuits the lamp L<2>. When the called subscriber disconnects himself, the relapse of relay 106 energizes relay 13 again in series with relay 101, lighting the lamp L<2>, and the operator takes down the plug from the jack j<1>, de-energizing relay 12, which opencircuits relay 101, which de-energizes relay 103, which energizes release magnet 112. P.B.X. operator's supervisory signals (lamps L<4> - - L<7>, Fig. 2.). Lamp L<6>, connected to the busy wire 95, is energized as long as the trunk 30, 31 is engaged. Lamp L<7> is lighted over wire 99 when the trunk is first seized, but as soon as the connector takes its first vertical step the lighting-circuit is transferred by off-normal contact 161 to wire 96 and lamp L<5>, the circuit of which in turn is opened by relay 106 when the called subscriber replies, but which lights up again when he disconnects himself. Lamp L<4> is lighted when the main exchange operator forwards a call to the P.B.X. operator to be dealt with, as described in the next paragraph. Incoming calls completed by the P.B.X. operator. When the branch exchange is asked for, the number of the particular wanted subscriber not being known to the caller, the main exchange operator presses the ringing-key K, which energizes relay 32, Fig. 2, which locks itself up and lights the call lamp L<4>. The P.B.X. operator throws her listening-key K<3>, which unlocks relay 32, energizes relay 33 (which looks itself direct to the grourded wire 97), and connects the impulse sender S<1> in the lower side of the trunk between coil 34 and the connector line relay, which is now disconnected from relay 13, Fig. 1, by relay 33. The relapse of relay 13 causes the extinction of lamp L<2> to indicate that the P.B.X. operator has answered. The desired connection is then ascertained and is set up by the sender S<1>, after which the key K<3> is restored. When the called subscriber answers, relay 106, Fig. 3, disconnects ground from wire 97, unlocking relay 33 which restores the metallic continuity of the lower side of the trunk, so that the supervisory signal L<2> at the main exchange is under control of the relay 106 as in the operations previously described. A release key K<4> is provided in the circuit of the sender S<1>. Outgoing calls handled by P.B.X. operator. A P.B.X. subscriber can connect himself to the P.B.X. operator over an idle service trunk by raising a connector to a particular rotary level. The P.B.X. operator then calls the main exchange by pressing the key K<2> of an idle trunk, connecting battery to wire 30 so as to energize relay 13, which locks itself up, and lights the call lamp L<2>. The relay 13 is unlocked by the sleeve relay 12 when the call is answered. When the wanted connection has been obtained, the P.B.X. operator calls back to the calling P.B.X. subscriber by a connector H. Outgoing calls made without the intervention of the P.B.X. operator. Alternatively, a. P.B.X. subscriber can raise a connector to a different rotary level bo connect himself directly to the first idle exchange trunk, in which case battery is connected to the circuit 94, 30 by the calling connector to energize the call relay 13. The calling connector grounds the busy wire 95 over terminal 151 so as to light the trunk busy lamp L<6> and to energize relay 100, which disconnects the trunk connector H and prevents lamp L<7> from being lighted, as it would be if the trunk had been seized for an incoming call.