Patent GB-247555-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1926-02-08
Abstract: 247,555. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Wicks, J.). Feb. 11, 1925, [Convention date]. Automatic exchange systems; partyline systems; metering.-In a system in which impulses are repeated from the first selector E to subsequent selectors, the choice between two sets of wipers in the connector is effected by a marginal relay controlled from the first selector over the a lead, and the supply of ringing current from the first selector is initiated by the ungrounding of the a lead at the connector when connection is made to an idle line. The impulses for operating the second selector E' and connector Hare repeated direct to the magnets of these switches over the b lead. The circuits of the switches E', H are further simplified by the use of two-step relays in the incoming test circuits to serve a double purpose, thus the relay 201, Fig. 2, serves as a release and switching relay, and the relay 301, Fig. 3, serves as a release and change-over relay. The first selector has associated with it two minor switches M<1>, M which respond to the first two digits. The switch M<1> determines which sets of wipers shall be used in the first selector and connector (the second selector has only a single set of wipers) by energizing or not energizing a relay 22 and by including or not including a resistance R in the circuit of the outgoing a lead. The switch M serves for party-line selection by determining which of five ringing frequencies shall be employed and to which leg of the wanted line it shall be applied. For an exchange of 4000 lines the second selectors may be omitted. Dialling the digit O sets the switch M<1> to its tenth position, in which it sets the selector E to its first level, which gives access to the operators' circuits. Reverting calls are made by dialling the digits 610 to connect the calling line metallically to an idle ring-back set RC in the tenth level of the selector E. The metallic switch-through is accomplished by a relay 12 controlled by the switch M<1> in its sixth position. It is arranged that a single accidental impulse shall produce a self-cancelling effect. First selector E. Relay 13 energizes relay 15 which energizes relay 17 and at 42 closes a dialtone circuit through condensers 138, 9<1>. The first digit is repeated to magnet 29 to set the switch M<1>, and on the relapse of relay 16, which is energized in parallel with magnet 29, relay 17 is unlocked, its original circuit having been opened at contact 79, so that the second digit is repeated to magnet 27 to set the switch M. The relapse of relay 16 at he end of this digit energizes relay 19, which Jocks itself and directs the third digit to the vertical magnet 25. Offnormal contacts 36, 37, 50, 128 are operated at the first step. Contact 50 energizes relay 20 which locks itself and prepares a circuit for rotary magnet 26 which is energized when relay 16 relapses. Magnet 26 unlocks relay 20 which is energized again from the test wiper if the first trunk is busy, and hunting proceeds in the usual way until an idle trunk is found, whereupon relay 21 being no longer short-circuited becomes energized, switches through to the selector E', grounds the test wiper 89 and energizes relay 16. Second selector E<1>. Relay 19 is now held over the outgoing a lead from ground at contact 210. The two-step relay 201 is energized only sufficiently to break contact 214. The fourth digit is repeated by relay 13 direct to vertical magnet 205. Relay 203 is energized from wire 264 at the first step and locks itself, and on the relapse of the series relay 202 the rotary magnet 206 is energized and unlocks relay 203. If the first trunk is busy, relay 203 is energized again from the test wiper and hunting proceeds asusual until :an idle trunk is found, whereupon, the upper winding of the two-step relay 201 'being no longer short-circuited, this relay becomes fully energized, switches through to the connector H and grounds the test wiper 243. Connector H. Relay 19 is now held in series with the upper winding of relay 305, which becomes energized or not, to bring into play one or other set of wipers of the connector, accordingly as the resistance R is not or is included in its circuit by the switch M<1>. The two-step relay 301 is energized only sufficiently to break contact 321. The fifth digit is repeated from the first selector direct to vertical magnet 307. The relapse of relay 302 at the end of the digit completes a circuit for the lower winding of the twostep relay 301, which becomes fully energized so as to lock itself and to direct the final digit to the rotary magnet 306. Busy signal. If the test relay 303 is energized from the test wiper it locks itself in preparation for the relapse of relay 302 and connects a busytone circuit 402 to the calling line through condensers 138, 9<1>, Fig. 1. Supply of party-line ringing current. If the line is idle. the relapse of relay 302 completes a circuit for the upper winding of relay 304, which locks itself and switches through. Relay 19, Fig. 1, is de-energized by the disconnection of ground from the a leg of the connection and completes a circuit for ringing current of selected frequency from the wiper 85 of switch M to either the a or b leg accordingly as relay 17 is or is not energized over the wiper 84. When the called subscriber answers. a metallic circuit is completed from ground 64 over the called loop and through the lower winding of the ringing cut-off relay 18, which locks over its upper winding and connects the called line to the feed relay 14, which de-energizes relay 16. Metering. A metering impulse may be sent over circuit 104 in the interval between the energization of relay 14 and relapse of relay 16, contact 44 being connected to booster battery instead of ground if this effect is desired. Release. When the calling subscriber hangs up, the relapse of relays 13, 15 energizes release magnets 24, 28, 30 and removes ground from wiper 89, thus unlocking relays 201, 301 which energize release magnets 204. 308. Reverting calls. The subscriber dials 610 followed by two digits signifying the appropriate combination of rings. The switch M' in position 6 connects relay 12 in parallel with the upper winding of ringing cut-off relay 18. When an idle ring-back set is found in the tenth level of selector E. relay 21 is energized and closes a circuit through the tenth-level spring 139 to energize relays 12, 18. Relay 12 disconnects the line relay 13 and switches the calling line metalically to the line relay of the ring-back set. This set feeds back ground to the holding circuit 157 104, responds to the two final digits, and then, when the calling subscriber has hung up, sends back ringing currents to ring the called and calling parties alternately until the called party answers. Calls to operator. In response to the digit O the switch M<1> in its tenth position closes a circuit through normal contact r28 for vertical magnet 25, so that the first selector is raised to its first level and hunts therein. Annulling the effect of a single impulse. A single impulse moves the switch M<1> to its first position and energizes relay 22. which closes a circuit for the release magnet 30, since the normal contact 79<1> is opened only at the second step of the switch M<1>. Specification 252,444 is referred to.