Patent GB-144252-A (GB)
Title: Improvements in or relating to automatic telephone systems
IPC: H04Q3/00
Filed: 1920-02-13
Abstract: 144,252. Automatic Telephone Manufacturing Co., (Assignees of Wicks, 1.) May 31, 1919, [Convention date]. Automatic exchange systems.-A single set of connectors handles the traffic between lines of several different types, such as (1) standard single-station lines, (2) common-battery party lines A, Fig. 1, (3) party lines E, Fig. 4, with local-battery magneto substations which transmit their switching- impulses over a simplex circuit, and (4) trunks to another exchange. Repeaters B, Fig. 1, D, Fig. 4, are connected between the lines A, E and their line-switches C, C<1>, but are omitted in the case of standard single-station lines. The wanted subscriber on a party line is called by a code ringing-signal, the exchange being provided with a single code ringing equipment S<1>, S, Fig. 3. and each con. nector H, Fig. 2, having a code selector M, Fig. 3, which is operated by the final digit to pick out a circuit giving the wanted signal. Reverting calls are dealt with by a number of ring-back sets N, Fig. 3, which also have access to the code ringing equipment through code selectors, and which send back a selected signal to the calling line. When a calling party-line subscriber transmits the two digits which signify a reverting call the connector selects the first idle ring-back set, which is then actuated by the third digit cliaracterizing the wanted party.Means are provided at the repeaters B, D for shunting out the repeatercoils while ringing-current is being transmitted, a clean metallic circuit being extended to the called station. Connexions are obtained to another exchange by calling a particular two-digit figure, in response to which the connector selects the first idle trunk. An exchange attendant can extend a test circuit to any subscriber's line by means of a special connector P, Fig. 5, which also disconnects the line from its associated relays and repeater. Call from party line A, Fig. 1, to party line E, Fig. 4. A relay 10, energized over the calling line, energizes relay 12 and bridges the repeater circuit 8, 20, 9 across the leads to the line switch C, which extends the call to an idle connector H, Fig. 2, in known manner. The impulses for. the first two digits are repeated by relay 10 to the line relay 30 of the connector, which moves its four wipers to the terminals of the wanted line 95, 98, the side-switch stepping forward at the end of each series of impulses under control of relay 39 and magnet 41. Busy test and signal. If the wanted line is busy there is ground potential on the connected test terminals 49, 50, so that magnet 41 is kept energized over wiper 47, to prevent the sideswitch from moving to its third position, and relay 48 is energized over wiper 56 to connect a busy tone circuit to the calling line. The calling subscriber either releases the connexion or waits until the wanted line becomes idle. Supply of code ringing current. If however the wanted line is idle, magnet 41 de-energizes in due course and moves the side-switch to its third position, grounding the test wipers and preparing a circuit 63, 40, 39, 38, 64, 65 by which the impulses of the third digit are repeated to the stepping magnet 66 of the code selector M, Fig. 3, which selects one of the code levels of the ring- ing) equipment S, S'. Each of the switches S, S' has two codes, associated respectively with its second and fourth levels, giving a choice of four signals 1-1-1, 1-1-2, 1-1-3 and 1-1-4, but the number of these switches and of the code levels in each switch may be increased to give any desired number of signals. It will be assumed that the code selector M has been set on its third set of terminals, connecting wiper 67 to a contact 108 which is connected alternately to ground and to a ringing-generator G by a relay 114 controlled by the fourth level of the switch S. The setting of the code selector M is followed by the energization, over circuit 76, of relay 75, Fig. 2, and also by the intermittent energization of the stepping magnet 86 of the switch S by the interrupter 81, Fig. 2, over circuit 85. At the next passage of the wipers of switch S over their first terminals, a circuit is closed through wipers 89, 68 to energize relay 105, Fig. 2, which locks itself up and completes a ringing-circuit 108 (Fig. 3), 67, 106 (Fig. 2), 104, 102, 99, 55, 98 (Fig. 4), relay 96, 95 (Fig. 2), 54, 93, 91, relay 84 to battery. The A.C. relay 96 responds and energizes a slow-release relay 116, which short-circuits the repeater D as long as ringing continues, extending a clean metallic circuit to the called line. When the called subscriber answers, relay 84, Fig. 2, is energized in the ringing-circuit, locks itself up, opens the ringing-circuit, closes the speaking- circuit, and opens the circuit 85 of the stepping- magnet 86, Fig. 3. On the de-energization of relays 96, 116, Fig. 4, relay 121 is energized over the two sides of the called line in parallel to ground at 129 and closes contact 123. Release. When the calling subscriber disconnects himself, relays 10, Fig. 1, and 30, 33, Fig. 2, relapse, and the connector release magnet 124 is energized. Relay 33 also closes a circuit for the stepping magnet 66 of the code selector M, Fig. 3, through its self-interrupting contact 126 and wiper 70 to restore this switch to normal. Calls to single-station lines. The operation is the same, the third digit of these lines being such that the simple intermittent ringing signal 1-1-1 is selected. Calls originated by the local-battery magneto party line E, Fig. 4. The impulse-senders 129 are connected in a simplex circuit through the two windings of the ringer 127 and the two sides of the line in parallel to the line relay 121. so as to reduce the resistance of the impulse circuit, which is apt to be unduly high in lines of this type. The relay 121 repeats the impulses to the connector in the same way as relay 10, Fig. 1. Reverting party line calls. In calls of this class, the first two digits bring the connector H, Fig. 2, to the first of several sets of terminals such as 130 - - 133 connected to ring-back sets such as N, Fig. 3. If the first set is busy, terminal 132 is grounded, so that magnet 41 holds the side-switch in its second position, but terminal 131 is connected to battery so that the busy relay 48 is not energized. Circuits are now closed by which the rotary magnet 44 and relay 48 alternately close and open each other's circuits, so that the connector advances until it finds an idle ring-back set, whereupon magnet 41 de-energizes and the side-switch passes to its third position. Relay 61 is now energized in a circuit through wiper 56, disconnects all the relays of the connector, switches the incoming trunk metallically to circuit 175, 190, so as to energize relays 142, 143, Fig. 3, and locks itself in circuit 191, 192. The third digit controls relay 142 to operate the stepping magnet 145 of the code selector associated with the ring-back set, so as to select a particular code signal circuit, as described in a previous paragraph, and on the termination of the impulses a relay 144 in series with magnet 145 relapses to energize relay 151. The stepping magnet of ringing-switch S or S<1> is now energized by interrupter 252 over wiper 154. The calling subscriber hangs up his receiver, de-energizing relay 142, and when the switch S or S<1> next passes over its first set of contacts a circuit is closed through wiper 153 to energize relay 163, which locks itself and extends the code ringing circuit from wiper 152 over conductor 175, 54 (Fig. 2), 174, 138, relay 15 (Fig. 1), 140 (Fig. 2), 172, 55, 190, 170 (Fig. 3), relay 169 to battery. The A.C. relay 15 energizes relay 182 which shunts out the repeater B as long as ringing continues. When the wanted subscriber answers the code call, relay 169 responds and unlocks relay 143, which relapses and closes a circuit 145, 184, 183, 155 for restoring the code-selector to its normal position. The de-energization of relay 143 also opens circuit 191, so as to unlock relay 61, Fig. 2, which energizes magnet 124, so that the connector is restored and disengages the ring- back set. The two subscribers on the line A can now converse, receiving current through coil 5 and relay 10. Trunking to another exchange. The interexchange trunks, such as 193 - - 196, Fig. 2, have the test terminal 194 connected to battery, in the same way as the ring-back sets, so that the connector, having been set on the terminals of the first trunk, continues to rotate if this trunk is busy until it finds an idle trunk, as described in the preceding paragraph. Attendant's test connector P, Fig. 5. The bank terminals of this switch are wired to points between the lines A, E, Figs. 1 and 4, and their repeaters B, D. When the test connector is set on the terminals of a busy line A, Fig. 1, the circuit of the third wiper is open at contact 14, Fig. 1, and nothing further happens, except that the attendant may converse with the subscribers through condensers 212, 213. But if the line is idle, relay 211, Fig. 5, is energized in series with relay 227, Fig. 1, which disconnects the line A from its repeater B and feeding-bridge 5, 10. Re. lay 211 locks itself in a circuit through the offnormal contact 224, bridges the condensers 212, 213 and disconnects the line relay 200. There is therefore a clean, unbridged, metallic circuit from the attendant to the line A, over which any necessary tests may be performed. The attendant releases the test connector by sending ring- ing-current which energizes an A.C. relay 230. The test connector may be reached through a selector and may be controlled by an operator at a main exchange.