Patent GB-177806-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1922-04-01
Abstract: 177,806. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Wicks, J.). April 1, 1921, [Convention date]. Automatic and semi-automatic exchange systemes. - Relates to the establishment of inter-exchange connections under the control of operators, and especially to a form of repeater set associated with the inter-exchange trunks, Fig. 6 shows the lay-out of a system comprising a manual first exchange connected bv trunks X to an automatic second exchange, which is connected by trunks X to an automatic third exchange. Local connections at the second and third exchanges are made automatically, by selectors such as E, F, H, but all interexchange connections are set up by an operator at the originating exchange, who may in some cases call in the assistance of an operator at the wanted exchange. The calling subscriber in all cases is asked to disconnect himself and is recalled when the wanted connection has been obtained. At the automatic exchanges each trunk such as Z terminates in a repeater set D<1>, where it divides into three branches, (1) to a jack J<8>, whereby an operator can deal with incoming calls or set up outgoing calls over the trunk, an auxiliary dialling jack J<9> being also employed in the latter instance; (2) to a selector E<2>, for setting up automatic connections under the control of incoming impulses; this branch also extends to a jack J', so that the selector E<2> can be controlled by a local operator; (3) to a particular level of the terminal banks of second selectors F<1>, which are only employed in setting up connections between the first and third exchanges. The tenth levels of the local first selectors E, E<3> are reserved for calling the trunk operators. The tenth levels of the trunk first selectors E<1>, E<2>, &c. give access to the trunk second selectors F<1>. The other nine levels of the local and trunk first selectors are multipled together. A connection from the first to the third exchange is made by calling the digits OZ, followed by the wanted subscriber's number, and extends over the route O, X, D, E<1>, F<1>, D<1>, Z, D<2>, E<4>, &c. Other exchanges (not shown) may be reached bv calling a different second digit to raise the selector F<1> to a different level. A call from the second to the third exchange is made, without calling any prefatory digits, over the route O<2>, J<8>, D<1>, Z, D<2>, E<4>, &c., or might be received by the operator at the third exchange at the jack J<10> and extended through the cord O<3> and selector E<4>. The repeater sets D, D<1>, D<2> are identical, though certain features of the repeater D are inoperative owing to the first exchange being manual. The talking circuit through each repeater set is normally discontinuous, but is completed on the arrival of the first digit. In the case of outgoing calls set up by a local operator the talking circuit extends through the operator's cord and not through the repeating set. Impulse transmission between exchanges is in all cases over a simplex circuit comprising the two sides of a trunk in parallel. Call from the first exchange, Fig. 1, to the third exchange, Fig. 5. When the operator at the first exchange plugs into the jack J<2> of an idle trunk X, a sleeve relay 35 is energized and energizes the busy signal 34 and a relay 27, which closes a simplex circuit over the two sides of the trunk in parallel to energize the relays 116, 117, Fig. 2, of the repeater D at the second exchange. The relay 117 grounds the wire 164 and energizes relay 115, which grounds the test wire 161. The relay 116 bridges the trunk 163, 165 through a resistance R<5> to prepare the selector E<1>, Fig. 3, for operation. The operator then plugs the dialling-cord P, Fig. 1, into the auxiliary jack J<3>, to connect her dial S in the circuit of the relay 27, and transmits the digits 02 followed by the number of the wanted subscriber. The first two digits are repeated by the relays 27, 116 to the trunk 163, 164, and the selectors E<1>, F\ Fig. 3. operate in the usual manner to make connection with the repeater D<1>, Fig. 4. asociated with an idle trunk Z to the third exchange. The switching relays of the selectors E<1>, F<1> are kept energized over the wire 164. During the transmission of impulses a relay 118, Fig. 2, is energized and cuts the resistance R' out of the impulse circuit. The relay 118 also energizes relay 112, which locks itself up, connects the trunk 163, 165 to the repeating coil T<1>, and energizes the cut-off relay 102, which energizes the busy signal 106. As soon as connection is extended to the repeater D<1>, Fig. 4, the relay 238 is energized over the circuit 232, 216, 164 and bridges the line relay 258 across the trunk 231, 233. The relay 238 also energizes relay 244, which energizes the cutoff relay 248. The line relay 258 closes a simplex circuit over the trunk Z to energize the line relay 303, Fig. 5, of the repeater D<2> at the third exchange. Subsequent digits are repeated by the relays 258, 303 to the trunk 304, 305 and operate selectors which complete the connection in the usual manner. Call from the first exchange to the second exchange. In this case the operator at the first exchange dials the number of the wanted subscriber without any prefatory digits. In response to the first digit, which may have any value except 0, the selector E<1> selects a local second selector, such as F, Fig. 6, and the connection is completed in the usual manner. Call from first exchange completed by operator at second exchange. Alternatively the operator at the first exchange, instead of transmitting impulses, may send ringing current over the trunk X to energize the relay 100, Fig. 2, which locks itself, lights the call lamp L<3>, and energizes relay 113 to ground the test wire 161. The operator at the second exchange answers with a cord O<1> and completes the connection by transmitting impulses from her dial S<2> over the trunk 163, 164 as described later. The relay 102, energized in the sleeve circuit, unlocks the relay 100 and energizes relay 113, which grounds the wire 161 and disconnects the line relay 116. The relay 112 is not energized, so that the talking circuit extends through the cord 0' and not through the repeater D. Similarly the operator at the third exchange may be called in to complete a connection at that exchange. In these cases, at the termination of the call, the originating operator transmits ringing current to energize a cord relay 150, Fig. 2, which locks itself and lights a supervisory lamp L<4> in front of the second operator. Call from second exchange to first exchange. The operator plugs a cord O<1> into the jack J<4> of an idle trunk X and transmits ringing current to energize the call relay 39, Fig. 1, which energizes the busy signal 34 and lamp L<2>. The relay 102, energized in the sleeve circuit, energizes relay 113, which grounds the test wire 161. When the wanted connection has been completed at the first exchange, the operator at the second exchange recalls the calling subscriber by plugging the other end of the cord O<1> in the jack J<6>, throwing the key K<3>, and operating her dial S<2>. Ground is first supplied to the wire 164 through the sleeve relay 110<1>, but a moment later the wire 164 is directly grounded by the relay 176, Fig. 3, and relav 110<1> is short-circuited. The connection is completed by the selector E<1> and local selectors. When the subscriber replies, the reversal of current at the connector energizes a polarized relay 159 which extinguishes the lamp L'. At the termination of the call. the operator at the second exchange sends ringing current over the trunk X to energize the cord relay 29 and lamp L<1> at the first exchange. Call from second exchange to third exchange. The operator plugs the left-hand end of a cord O<1>, Fig. 2, into the jack J<8>, Fig. 4, of an idle trunk Z. The relay 248, energized in the sleeve circuit, energizes relay 266, which grounds the wire 232 and closes a simplex circuit over the trunk Z to energize the line relay 303 of the repeater D<2> at the third exchange. The operator then plugs her dialling cord P<1> into the auxiliary jack J<9> and calls the wanted number on her dial S<1>, which is in circuit with the relay 258. As long as the dial is off normal, a contact 145 energizes relav 244, which opens the contact 246, leaving the simplex circuit dependent on the contact 259 of relay 258. The impulses are thus repeated by relay 258 to the third exchange to complete the connection. When the subscriber replies, the operator inserts the other plug of the cord O<1> in the jack J', and recalls the calling subscriber by operating the selectors E<2>, F, H, Fig. 6, over the trunk 255, 257 by means of her dial S<2>, as previously described. Calls originated by the third exchange. These are dealt with in a similar manner. As will be seen from Fig. 6, a call to the first exchange is completed by the selectors E<2>, F<1> in response to the digits 01. When the selector F<1> seizes the trunk X over the wires 160, 162, the relay 110 is energized over the wire 161 and energizes relay 114, which closes the circuit of the cut-off relay 102, which energizes the busy signal 106. Ringing current is then transmitted from the third exchange to energize the call relay 39, Fig. 1.