Patent GB-215299-A (GB)
Abstract: 215,299. Compagnie GÚnÚrale de TÚlÚ- graphie sans Fil. May 5, 1923, [Convention date]. Automatic exchange systems; impulse-transmitters.-In a small exchange simultaneous calls are provided by an arrangement whereby the line relays lock up over a chain circuit including the locking contacts of all the preceding line relays. The invention is described as applied to a relay switching system comprising sixteen substations divided into four groups A - - D of four substations. A called substation A4, Fig. 4, is connected to a wanted substation C1 over an idle link CR1, CR2, &c., Fig. 2, the wanted line being marked out by a counting relay set C1 - - C4, Fig. 3, which operates successively in response to two series of impulses, first to select the wanted group C and then to pick out a marking circuit individual to the wanted line within this group. In the system illustrated, the change-over between the two impulse series is effected by a variation in the resistance of the calling loop, but the system may be adapted for change-over by the usual pause between impulse series. Means are provided for keeping all the calling dials except the calling subscriber's locked when the switching apparatus is engaged in setting up a call or when all the links CR1, CR2, &c. are engaged. The same vibrator Vib, Fig. 1, is used for ringing the called party and for transmitting " busy," " no reply," or " fault " tone to the calling party, arrangements being provided whereby if the called party does not reply within a certain interval, or if the calling party omits to dial or only partially dials, a warning tone is transmitted from the same source and both the counting and marking apparatus and the linkconnecting apparatus released. Means are also provided whereby a warning tone is given to the calling party and the switching apparatus released if a number greater than the exchange capacity is dialled. Provision is made for preventing interference due to simultaneous calls. Construction of impulse transmitter. This comprises an impulse wheel R1, Fig. 4, and a finger dial RC mounted upon a common shaft. The finger holes of the dial RC are marked with the group letters as well as with numbers. The nose of the armature 5 of a relay T, arranged in series in the subscriber's loop but normally shortcircuited over contacts 4, 10, is normally in the path of a cam d on the periphery of the finger dial RC, and, unless the receiver R has been removed from the switch-hook and also the relay T is energized, prevents rotation of the finger dial RC. Selection of a wanted subscriber's marking circuit. On a calling subscriber A4, Fig. 4, removing his receiver, his line relay A, Fig. 2, is energized over the calling loop, locks up over armature 61 in a chain circuit including the locking armatures of preceding line relays, and completes a series circuit over armature 60 for the impulse and change-over relays i, I, Fig. 3, both of which respond since the substation relay T is at this time short-circuited over contacts 4, 10. The response of the change-over relay I is without effect, but the impulse relay i energizes a relay i<1>, which at armature 72 closes a circuit for a relay Q<1>, Fig. 4. Relay Q<1> locks up and energizes a relay Q which closes parallel circuits for group cut-off relays Q1, Q2, &c., which by opening the initial energizing circuits of all the line relays A prevent the setting up of another call until the one in question has been dealt with. Simultaneous calls are prevented since the calling line relay opens the locking circuit of all subsequent line relays. The relay i<1> also energizes a relay ARM which locks up and prepares a circuit for a relay Mn. The calling party now dials the letter C (three impulses) denoting the group to which the wanted subscriber C1 belongs. On the first movement of the finger dial RC in the direction of the arrow F, the cam d opens the contacts 4 and removes the shunt across the relay T, which is energized if the switching apparatus is free, and permits the cam d to pass the stop. (If the switching apparatus were engaged in setting up a call the circuit over the calling loop would be disconnected at armature A4 of the cut-off relay Q1. The relay T would therefore not energize when the contacts 4 are opened and the finger dial would remain locked.) The short-circuit across the relay T is replaced directly the cam d passes the locking catch, but is again removed when the cam engages contacts 10, which remain open until closed by the cam on the return movement of the dial after the dialling impulses have been transmitted. The resistance of the relays i, I is so proportioned that the relay I only responds when the relay T is short-circuited. The return movement of the impulse wheel R1 interrupts the line circuit at contacts 11 three times, causing the relay i to relapse and transmit three current impulses to the relay Mn. At the first impulse the first counting relay C1 is energized over armatures 101, 107, locks up, prepares the circuit of the second relay C2, and closes a circuit over armature 114 for a relay J. The relay IT also energizes over armatures 100, 109, locks up over its armature 102, and prepares a circuit for a relay 2T, which is energized and locks up when the relay Mn relapses at the end of the first impulse. At the second impulse the second relay C2 energizes over armatures 101, 107, 112, locks up, and prepares the circuit of relay C3. A relay 4T also responds over armatures 101, 106, and unlocks relay IT. The relay 2T remains energized over armature 108 until the relay 4T is de-energized by the relapse of the relay Mn. On the next response of the relay Mn at the third impulse, the third counting relay C3 and the relay IT are locked up, the relay C3 preparing a marking circuit over the leads LE, LC. After the third and last impulse has been sent by the impulse transmitter, the cam d on the finger dial closes the contacts 10 and short-circuits the relay T. The relay I now pulls up and the selected marking wire LC is connected to battery over a resistance RP and armatures 40, 39, energizing a marking relay CGC, Fig. 4, which locks up in series with a relay P, Fig. 3, and connects up the marking wires C' - - C' of the subscribers in the wanted group. The resistance RP maintains a sufficient potential difference between the relay CGC and the negative pole, to permit the relay P to operate and energize a relay O, which by disconnecting battery at armature 110 restores the counting apparatus to normal. The relapse of relay C1 de-energizes relay T, thereby energizing a relay K, which locks up, de-energizes the relay O, and completes a circuit for a switch over relay K<1>, which connects the marking wires C<1> - - C<4> of the wanted group to the counting relay marking wires LA, LB, &c. The subscriber now dials the digit 1, in response to which the first counting relay C1 locks energized, closes the circuit of relay J and prepares a marking circuit over the leads LE, LA, C<1>. After this impulse the relay T is again shunted at the contacts 10, and the relay I pulls up and completes at armature 40 the selected marking circuit over which the marking relay CP, Fig. 2, of the wanted substation is energized. A relay L, Fig. 1, is also energized over a circuit 73, 41, 75, and closes a circuit for a release preparing relay PZ, Fig. 3. The relay P does not operate at this time since the resistance RP is shunted at armature 74 of relay K. The change-over relay I may be adapted to respond due to a pause at the end of the impulse series instead of to a variation in the resistance of the subscribers' loop. In this case the relay I is made slow-to-act so that it only responds during the pause after each impulse series, over contacts of the relays i, C1. Busy test, busy tone, and busy release. If the called party is engaged in a call, say over the link CR1, Fig. 2, his feed relay D is energized, and a circuit is completed over the marking wire C<1>, contact 17, and lead PL for relays X, W, Fig. 1, (over armature 95), and for the calling party's marking relay CP (over lead CA). Relay CP connects one side of all the associated link connecting relays F to battery over armature 14, but only the relay associated with the first idle link CR2 is energized over a relay G2, a back contact of the armature 36 of the relay PH2, and a front contact of the armature 36 of the relay PH1, which was energized when the link CR1 was taken into use. The relay G2, which is connected in parallel with all the connecting relays F of the link CR2, locks up over its armature 27, and the calling line is extended over the link CR2 and the conductors A1, A2, to the ring- ing vibrator Vib, which is set in operation over the armature 117 of a relay U, energized over the armature 28 of the relay G2. The relay W connects a potentiometer across the ringing leads A1, A2, and reduced ringing current is transmitted to the calling party to inform him that the wanted line is busy. The calling line feed relay D is energized over the armature 13 of the connecting relay F, locks up, de-energizes the line and marking relays A, C, P, and completes a holding circuit for the relay F in series with a relay H2, Fig. 1, which marks the line CR2 busy. The relapse of the line relay A opens at armature 60 the circuit of the relays I, i. The relay i<1> then de-energizes and completes a circuit for a release relay Z which restores all the counting apparatus. The link circuit CR2 is released when the calling subscriber hangs up or automatically by the timing magnet MA after a given interval, as described later. Ringing. If the wanted line is idle, the marking relay CP is energized and a connecting relay F and a relay Gl extend the wanted line to the ringing conductors A1, A2 over an idle link CR1, as described in the previous paragraph with reference to the extension of the calling line ove