Patent GB-276656-A (GB)
Title: Improvements in and relating to telephone systems
IPC: H04Q3/00
Filed: 1927-08-11
Abstract: 276,656. Associated Telephone & Telegraph Co., (Assignees of Wicks, J.). Aug. 26, 1926, [Convention date]. Automatic and semi-automatic exchange and party line systems; metering.-The vertical magnet of a local selector (or the repeating relay of an incoming selector repeater) receives current as soon as the selector is seized over the talking wires in series with a bridged "holding relay" of high resistance in a previous selector repeater, this relay being short-circuited by theimpulse relay of the selector repeater to operate the magnets (or repeating relay). The invention is described with reference to the establishment of local, distant and toll calls to ordinary and party lines and to private branch exchanges. In the following description, the hundreds digit of a reference numeral indicates the figure in which it is to be found. First selector repeater, Fig. 1. Release relay 127 energizes the holding relay 128 which locks itself over 161, 148, 136, 128 (upper) 152, 129, 133. Relay 126 at 143 repeats the first digit to the series relay 129 and magnet 133 by shortcircuiting relay 128 and resistance 136, armature 142 in its back position making a holding circuit for relay 128 (lower). At the end of. the digit, the rotary magnet 134 interacts in the usual way with stepping relay 131 and relay 132 switches the talking wires through and extends the grounded holding wire 122<1> to the test wiper. Modified first selector repeater, Fig. 9. The series relay is replaced by a relay 929 which is short-circuited between impulses and keeps the holding relay 928 steadily energized over its upper winding during impulsing. Otherwise the selector differs from that shown in Fig. 1 only in the metering and attendants' signalling arrangements described below. Intermediate selectors, Fig. 2. When the selector S<2> is seized, relay 201 is operated partially over its upper winding and pulls up armature 210. Relay 126 repeats the next digit to series relay 202 and magnet 204 by short-circuiting relay 128 (upper) and resistance 136. At the end of the digit, stepping relay 203 and magnet 205 interact in the usual way and when an idle selector S' is found, the lower winding of relay 201 is no longer short-circuited and the relay pulls up all its armatures to extend the talking and test wires to selector S<3> which is operated in an indentical manner and seizes a connector. Simple connector Fig. 3. Relay 301 pulls up its armature 312 when energized partially over its upper winding and the incoming test wire, and switching relay 305, also energized over the test wire, connects up the vertical magnet 306 which is controlled by relay 126 in the same way as the magnets of the preceding switches. At the end of the tens digit, relay 305 which, after the change over of springs 333 has been held by the series relay, connects up the rotary magnet 307. At the end of the units digit, relay 301 is energized fully over rotary springs 331 and cuts off the operating magnets whereupon relay 128 replaces itself by back-bridge reversing relay 130 and completes the talking circuit as far as the first selector is concerned. Busy test and signal. If the line is busy, relay 304 which pulls up as soon as the line is encountered remains locked up on the relapse of the series relay and connects up the busy generator BM. Ringing current. If the line is idle, relay 304' does not pull up and on the relapse of the seriesrelay, relay 305 pulls up in series with the cutoff relay 361, locks itself over its lower winding,. grounds the c-wiper and sends out ringing cur. - rent over relay 303. When the called party replies, relay 303 completes the connection. Release. Relapse of relay 127 when the ..calling party hangs up energizes the release magnet 135 and disconnects ground from the holding wire to release the switching relays 201, 201', 301 which energize their release magnets. The release magnets of the intermediate selectors isolate their test wipers. Party line connector, Fig. 7. This is operated in the same way as the simple connector except that relay 704 instead of the switching relay is energized initially to connect up the vertical magnet, and the dialling relay 705 is in parallel with the magnets. If the line is idle, the switching relay 706 in addition to its usual functions extends the impulsing circuit to the magnet 773 of a switch FS which, in response to an extra digit selects a ringing generator of appropriate frequency and over its later terminals energizes relay 704 to cause the ringing current to go out, on the relapse of the dialling relay, over the upper instead of the lower wire. The two step relay 701 is in this case energized completely over off-normal springs on the switch FS at the end of the extra digit and connects up a ring back tone 790. Had the line been busy, relay 701 would have pulled up after the second digit over 719 of the busy relay 702. Rotary connector, Fig. 8. This is operated in a similar manner to the simple connector, but the busy relay 806 is connected up by an extra sluggish relay 805 energized by the series relay 804 and if the first line is busy prepares a circuit for a stepping relay 803 which, on the relapse of relay 804, pulls up over an extra terminal 848 jumpered to the regular test terminal, holds relay 805, and locks itself over interrupter springs of the rotary magnet 809 which it energizes. The rotary magnet and stepping relay interact in the well-known way until, if all trunks are busy, the extra wiper encounters the last terminal 848<1> which is not connected to the ordinary test terminal. Relay 803 being unable to pull up, relay 805 falls back, locking the busy relay 806 and energizing the lower winding of relay 801 to make it pull up all its armatures and send back busv tone from 891. When an idle line is found, the relapse of relay 805 energizes switching relay 807 and the line is rung as in the case of the simple connector. Metering. Back-bridge relay 130 energizes the meter 116 and series relav 129 which locks itself and the meter to the release wire. Alternatively, back-bridge relay 930 connects booster battery to the private wire and releases sluggish relay 929<1> which restores the normal ground connection. Reverting calls on party lines. The first selector repeaters in one level give access to ring-back switches, Fig. 10, in which relays 11, 7 pull up. The next digit operates the vertical magnet 17 and parallel relay 13 which holds relay 11 until the end of the digit after springs 57 change over. The next digit operates rotary magnet 18 and the relapse of relay 13 connects relays 11, 15 to wipers 61, 62 and, over 90, energizes relay 12, which locks up, disconnects release relay 7 and energizes relay 14 over the release wire to make a new circuit for relay 7. Relay 925 which is not energized in series with the various switching relays in a normal call is able to pull up in series with relay 14 and now connects the talking circuit metallically to the switch RV and cuts off line relav 926 to release the release relay 927 which removes the holding ground from wiper 972. Relay 8 being no longer short-circuited by this ground now pulls up in series with relay 14, puts a new ground on the holding wire which has temporarily been grounded only over its lower winding, locks itself and connects up the feed relay 6 which pulls up over the loop, makes a new circuit for relay 7 and releases relay 14. When the subscriber hangs up, relay 6 falls back and energizes relay 5 which holds relay 7. Ringing current is now sent out alternately to operate both bells. Assuming for example that the switch is set to the terminals 81 - - 84, relays 11, 15 are operated by the interrupter 85. Relay 74 under control of interrupter 86 connects alternate battery and ringing current of various frequencies to the banks of wipers 63, 64, during each make and break period of 85. In the case assumed therefore, ringing current is sent via relay 10 from Glover the upper wire alternately with ringing current also via relay 10 from G2 over the lower wire. When the wanted party replies, relay 10 energizes relay 9 which cuts off the ringing current and relay 7 energizes release magnet 19 and releases relay 5 to replace relay 6 across the trunk. Relay 6 prevents relay 7 from falling back. When 'both subscribers hang up, relays 6, 7 fall back followed by relays 12, 8, 9, 11 and relays 932, 925, 907. Relay 925 energizes the release magnet 935. If the called party does not reply, the caller takes his receiver off to operate the ring- trip relay and replaces it to release the switches. Incoming selector repeater, Fig. 4. This is taken into use over the junction by a first selector repeater, or, if at a sub-office, by a second selector and relay 403 pulls up in series with relay 128 and relay 405 (upper) (the latter not being operated in this circuit) and is followed by release relay 408 and holding relay 406. Each time relay 128 and resistance 136 are short circuited by the second digit, the current in relay 405 is sufficiently increased to cause its operation to short circuit relay 406 thus repeating the digit to series relay 409 and vertical magnet 412. At each energization, relay 405 cuts in an opposing winding to make itself quick releasing. The relapse of the series relay energizes the rotary magnet 414 which interacts in the usual way with stepping relay 407. When an idle selector is found, switching relay 411 extends the talking wires and grounds the test wiper. Subsequent digits are repeated by relay 405 by shortcircuiting relay 406. On the second step of relay 301 (701 or 801) in the connector, relay 406 is released and relay 404 pulls up, connects up the back bridge relay 410 and disconnects relay 405 from the incoming junction wires, substituting a high resistance bridge 403, 442, 443 and at the same time removing a shunt provided for improving the impulsing circuit, from relay 403 which continues to hol