Patent GB-177154-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1922-02-25
Abstract: 177,154. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Willis, B. D.). March 16, 1921, [Convention date]. Automatic and semi-automatic exchange systems; party-line systems.-A system is described comprising a manual exchange, Fig. 1, and two small community automatic exchanges or C.A.X.s. The nearer C.A.X., shown in Figs. 2, 3 and 4, is connected to the manual exchange by two-way trunks such as 24, 25. The more distant C.A.X. has no direct connection with the manual exchange but is connected to the near C.A.X. by two-way trunks such as 260, 261, Fig. 4. Local C.A.X. connections are established by connectors such as H<1>, Fig. 3, which also act as rotary connectors, in response to particular first and second digits, to select an idle trunk to the manual exchange or to the distant C.A.X. Incoming calls from the manual exchange are established by connectors such as H, Fig. 2, which can also act as rotary connectors to select an idle trunk to the distant C.A.X. The invention comprises the following features. The connectors H, H<1> are provided with a pair of line relays, such as 28, 29, Fig. 2, in place of the usual double-wound relay, so that the operator or calling subscriber can, by operating a key to ground the calling line, keep one relay energized while de-energizing the other, thereby energizing a third relay to supply ringing current to the wanted line. In the case of calls to a party line the operator or calling subscriber operates the ringing key in accordance with the wanted subscriber's code. Means are provided for enabling reverting calls to be effected. The connectors are so organized that if the calling line has a ground leak sufficiently serious to interfere with its ringing or release functions, the connector is prevented from operating. In the case of local C.A.X. calls the current in the calling line is not reversed when the called subscriber answers, but whenever a call is established between two exchanges reversal takes place. In the case of calls to the distant C.A.X., this is effected by repeaters D, Fig. 4, at the incoming and outgoing ends of the trunks 260, 261. The repeaters D serve also to repeat the ringing control currents from one exchange to the other by grounding the trunk 260, 261 when the operator or calling subscriber presses the ringing key. Call from manual exchange to a party-line subscriber A<1>, Fig. 4, at the near C.A.X. When the operator plugs into the jack J<1>, Fig. 1, a jack-spring 16 bridges a polarized relay 17 across the trunk 24, 25 to energize the line relays 28, 29 of the connector H, Fig. 2, and the relay 29 energizes the relay 30. The operator throws the key K<1> to the left to bridge the dial S in place of the relay 17 and calls the two digits of the wanted number. The first digit is repeated to the series relay 31 and vertical magnet 48 in a circuit 47, 51, 56, 54 (or 56, 55, 53), 44. This circuit includes a back contact of the relay 28 as well as of the relay 29, so that the connector is not operated if there is a ground leak on the calling trunk sufficient to prevent the relay 28 from de-energizing. At the first impulse the relay 31 becomes energized and cuts out the line relay 28, substituting the resistance R to give an improved dialling circuit. After the first digit the relay 31 relapses and the second digit is repeated to the series relay 32 and rotary magnet 69. At the first impulse the relay 32 becomes energized and energizes the relay 34, which connects the test wiper 78 to the test relay 33. The relay 32 also cuts the resistance R in parallel with the line relay 28. If the wanted line is busy the relay 33 becomes energized in series with the relay 34 when the relay 32 relapses. The relay 33 locks itself and completes a busy signal circuit at contact 63. If, however, the wanted line is idle, the relay 33 does not become energized, the relay 34 relapses after the relay 32, and the switching relay 35 becomes energized in series with the cut-off relay 203, Fig. 4, of the wanted line. Party-line non-automatic code ringing arrangements. The operator rings the code of the wanted subscriber by throwing her key K<1> to the right, thereby directly grounding the trunk wire 24 and grounding the wire 25 through a resistance R<10>. By this means the relay 28 is kept energized while the relay 29 is de-energized, so that every time the key is thrown a circuit 47, 51, 42, 71 is closed for the relay 34, which connects ringing current to line. In the firstnon-ringing interval after the called subscriber answers, the back-bridge relay 27 becomes energized and reverses the connections of the relays 28, 29 to the trunk 24, 25, so as to energize the polarized relay 17, Fig. 1, which bridges an inductance 18 across the cord O to energize the relay 11 and extinguish the lamp L<2>. If the ringing key is again operated the relay 29, being now directly short-circuited instead of through the resistance R<10>, de-energizes comparatively slowly, but this is of no consequence as the subscriber has answered. Supervisory signals; release. When the subscriber A<1> disconnects himself the relapse of relay 27 again reverses the current in the trunk 24, 25 to de-energize the polarized relay 17, which opens the oridge 18 across the cord O to de-energize the relay 11 and light the lamp L<2>. The operator takes down the cord and the relapse of relays 28, 29, 30 energizes the connector release magnet 49. Local C.A.X. call. A calling subscriber A<1> is connected bv his line switch C to a local connector H<1>, Fig. 3, which operates in a manner generally similar to the incoming connector H, the line relays 115, 113 corresponding to the relays 28, 29. The first digit is repeated to the series relay 117 and vertical magnet 149, and the second digit to the series relay 118 and rotary magnet 150. As in the previous case, the connector cannot be operated at all if there is a serious ground leak on the calling line. The resistance R' corresponds to the resistance R, Fig. 2. During the second digit the relay 118 energizes a relay 119, which connects the test wiper 163 to one end of the upper winding of the switching relay 121. On the relapse of the relay 118 the otler end of this winding is connected to ground, so that if the wanted line is busy the relay 121 is short-circuited, and the relapse of the relay 119 a moment later energizes the relay 116, which locks itself and sends back a busy signal. If, however, the wanted line is idle the switching relay 121 is energized over the wiper 163 and locks itself up. Control of ringing current by calling subscriber. The subscriber A<1> rings the selected line by means of a key P, which grounds the a side of his line directly and the b side through a resistance R<7>. The relay 115 is thus kept energized while the relay 113 is de-energized, and the relay 112 is energized in a circuit 130, 131, 137, 136, 145, 118, 112, 138, 155, 150. This circuit also includes, but is of too high resistance to energize, the relay 118 and rotary magnet 150. The relay 112 connects ringing current to line and keeps the release relav 114 energized. In the first non-ringing interval after the called subscriber answers, the back-bridge relay 116 is energized. It will be noticed that in a local connector such as H<1> this relay is not arranged to reverse the current in the calling line. Reverting party-line calls. In the moment following the de-energization of the relay 118, Fig. 3, and while the relay 119 is still energized, that is to say in the moment when the connector H<1> is testing the line to which it has been set, a resistance R<4> is connected in the release wire 102, which sufficiently raises the potential on the test terminals of the calling line to enable the connector to seize that line in case the call is a reverting one. In such case the switching relay 121 at once becomes energized and the back-bridge relay 116 immediately thereafter. The calling subscriber then operates the key P to control the supply of ringing current from the connector to his own line. Call from the near C.A.X. to the manual exchange. A local connector H<1> is set by two particular digits to the first of the several trunks leading to the main exchange, and then operates as a rotarv connector to find the first idle trunk. The terminals engaged by the two test wipers 163, 162 are strapped together in the case of all these trunks except the last. On the relapse of the relay 118 after the second digit, the relay 121 is short-circuited, as previously described, if the first trunk is busy, and a circuit is closed through the extra wiper 162 for a relay 120, which keeps the relay 119 energized and co-operates with the rotary magnet 150 to rotate the connector. If all the trunks are busy the connector comes to rest on the last of them and sends back a busy signal as soon as the relay 119 relapses, but if an idle trunk is reached, such as 24, 25, Fig. 2, the switching relay 121 is energized over the wiper 163 and wire 89 in series with the relay 26, Fig. 2, which disconnects the trunk from its batterv connections in the associated connector H and extends it over wires 88, 90 to the bank terminals of the local connector. The calling subscriber presses his ringing key to transmit ringing current from the connector H<1> to operate the call signal 15, Fig. 1, and the operator completes the wanted connection by a cord O. The normal batterv connections of the trunk in the connector H are reverse with respect to those of the back-bridge relay 116 of the connector H<1>, so that when the calling subscriber disconnects himself and releases the connector H<1> the polarized relay 17, Fig. 1, which is energized during conversation, relapses and causes the lighting of the supervisory lamp L<2>. Call from manual exchange to the distant C.A.X. The trunks such as 260, 261, Fig. 4, between the near and distant C.A.X.'