Patent GB-175961-A (GB)
Abstract: 175,961. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Ray, A. J.). Feb. 23, 1921, [Convention date]. Automatic exchange systems; party-line systems.-A repeater D, Fig. 4, associated with a subscriber's line, is cut out of circuit, during the supply of ringing current to the line, by a relay 286, which is energized by direct current superposed on the ringing current but which is of too high resistance to permit the energization of the ringing cut-off relay. The invention is described in connection with a party-line system in which each connector H, Fig. 2, is associated with a code ringing-set F, K, Fig. 3, which responds to the last two digits of the called number and repeatedly transmits a corresponding code signal; for example, if the last two digits are 45 each code signal consists of 4 rings, a pause, and 5 rings. In the intervals between the code signals a characteristic tone is connected to the called line, so that if another subscriber on the same line lifts his receiver to initiate a call he will be warned off bv hearing either the code call signal or the special tone. For this purpose the substation equipment of a partv-line subscriber is arranged so that when the receiver is lifted the switch-hook only rises far enough to connect the receiver to line through a condenser, being retained by a catch N, Fig. 1, which may afterwards be tripped to allow it to rise fully. Means are provided for preventing a mutilated code signal from being sent to line in case the called subscriber answers or the calling subscriber disconnects himself in the middle of a code signal. The subscribers' dialling impulses are transmitted over a. simplex circuit. Connection to wanted line by selector-repeater B, Fig. 1, and connector H, Fig. 2. The calling circuit is completed through the dial 85, the two sides of the bell 22 and of the calling line in parallel, and the line relay 6. In response to the first digit the selector B operates in the usual manner to extend the call to an idle connector H, and the switching relay 8 closes a loop circuit to energize the line relay 100 of the connector. The second and third digits are repeated by the relay 6 to the connector, which operates in the usual manner to extend the call to the wanted line, and if this line is idle the relays 117. 116 are energized and the impulse repeating circuit is extended over wire 176 to the code ringing selector F, Fig. 3. Operation of the code ringing equipment, Fig. 3. The fourth digit operates the vertical magnet 201 of the code selector F, and at its termination the relapse of the slow-release series relay 202 extends the impulse circuit 176 to the rotary magnet 203, which is operated bv the fifth digit. At the commencement of this digit a series relay 204 energizes a relay 205, which locks itself to the grounded wire 173 and opens the original impulse circuit of the magnet 203, so that the relapse of relay 204 at the termination of the digit leaves the impulse circuit open. The relay 205 also closes the starting circuit 239 of a common interrupter I, consisting of three relays 261, 262, 263. All these relays are momentarily energized, but it will be seen that each relay opens the circuit of the next in cyclical order, so that the three relays continue to energize and de-energize in rotation, at a rate determined by the slow-release nature of the relays 262, 263, and the circuit 213 is intermittently grounded to energize the stepping magnet 214 of the switch K. When the wipers of this switch arrive on their first contacts a circuit is closed through the wipers 237, 236 in series to energize the relay 231, which locks itself, connects the interrupter circuit 213 to the ringing relay 217, and grounds the wire 175, which is connected through the ringing cut-off relay 125 to the upper outgoing talking wire 147. The relay 286, Fig. 4, is energized in this circuit to cut out the repeater D of the called line, but the resistance of the relay 286 is too great to permit energization of the relay 125. At each succeeding closure cf the interrupter circuit the relay 217 is energized and connects the ringing generator G over wire 174 to the lower outgoing talking wire 148, to @ing the bells at all the substations on the party line, the current returning through the condenser 290 and wires 147, 175. At each opening of the interrupter circuit 213 the magnet 214 steps the switch K forward, and when the wiper 236 arr:ves on a terminal wired to the terminal selected by the wiper 234 of the switch F, a relay 232 is energized and opens the circuit of the ringing relay 217. Ringing is resumed, however, when the switch K moves to its next terminals and continues intermittently until the wiper 236 arrives on a terminail wired to the terminal selected by the wiper 235 of the switch F, whereby the relay 231 is short-circuited and unlocked and opens the circuit of the ringing relay. The de-energization of the relay 231 also de-energizes the relay 286, Fig. 4. It will be seen that in this way two sets of rings are given, separated by a pause, and the wiring of the terminals of the wiper 236 to the terminals of the code selector F is such that the number of rings in the first set corresponds to the vertical setting of the switch F and the number of rings in the second set to its rotary setting. At non-ringing moments, when the relay 217 is de-energized, a tone machine Y is connected to the called line in place of the ringing generator G. When the switch K arrives on the first terminals of the second half of its bank the relay 231 is energized again and the code signal is repeated, and so on, until the wanted subscriber replies, whereupon, at the next de-energization of the relay 286, i.e. at the next termination of a complete code signal, the relay 281 is energized in a simplex circuit over the called line and bridges the wires 147, 148 metallically through the repeater coils 277, 278. Since the relay 231 is at this time deenergized, battery is connected across the wires 175, 174, i.e. across the wires 147, 148, and the ringing cut-off relay becomes energized. The relay 125 locks itself up, completes the talking connection, and unlocks the relay 205 so as to stop the interrupter I and switch K. Release. When the calling subscriber disconnects himself the selector B is released in the usual manner, and the relapse of the connector release relay 101 completes a circuit for the release magnets 190, 221 of the connector H and code selector F. This circuit includes a back contact of the relay 205, so that if the calling subscriber disconnects himself in the middle of a code signal, the wanted subscriber having failed to answer, the release is delayed until the relay 205 becomes de-energized, which occurs when the wiper 237 next arrives at its normal ungrounded position. In the meantime the relay 205 keeps the wire 173 grounded to lock the relays 117, 116, so as to mark the connector busy at the contact 132.