Patent GB-201162-A (GB)
Abstract: 201,162. Aktieselskabet Elektrisk Bureau. July 18, 1922, [Convention date]. Autom tic exchange systems in which a connector comprises a single coordinate tens switch the contacts of which are connected to similar units switches, are provided with means comprising two slow-acting relays whereby the releasing circuit of the tens switch is held open while the units switch is releasing, but is closed when the units switch reaches its normal position. The invention is described as applied to an exchange of 1000 lines. Line switch. When the calling subscriber lifts his handset, relay R<1>, Fig. 2, energizes and completes the circuit of rotary magnet M<1> of the line switch F, V which hunts for an idle group selector I, G, V. When an idle selector is found relay R<2> energizes in series with relay R<3>, breaks the rotary magnet circuit, short circuits a part of its winding to mark the group selector busy, and extends the talking circuit to the group selector. Group selector. This consists of a numerical switch and ten hunting switches, all of single coordinate type. Relay R<4> energizes and energizes relay R<5> which connects a source of alternating current to the other winding of relay R<4> to send dialling tone. When relay R' falls back on the first impulse slow release relay R<6> energizes and remains so during the whole of the digit. Contact 14 of relay R' sends impulses to the rotary magnet M<2> which advances the wipers in accordance with the digit dialled. At the end of the digit relay R<6> falls back and completes a circuit from commutator C to the rotary magnet M<3> of the selected hunting switch which hunts for an idle connector. When the test wiper of the switch finds an idle terminal, relay R<7> energizes, short circuits a part of its winding to mark the connector busy, opens the circuit of magnet M<3> and extends the talking wires to the connector. The circuit for relay R<7> includes the lower winding of relay R<18> at the connector which however is not at this stage energized sufficiently to pull up. Connector. Relay R<9>, Fig. 3, and sluggish relay R<10> energize in series. Relay R‹ energizes relay R<13>. The first release of relay R<9> when the tens impulses are received energizes slow-release relay R<14>. Impulses are delivered from contact 26 of relay R<9> to the rotary magnet M<4> of the tens switch. At the end of the digit, relay R" falls back, opens the circuit of magnet M<4> and energizes the switch-over relay R<18> which locks up over offnormal contact k<1> of the tens switch and switches over the impulse circuit to the rotary magnet M<5> of the selected units switch. Units impulses reenergize relay R<14> and are repeated from contact 26 to the units rotary magnet M<5>. Busy test and signal. At the first units impulse relay R<21> energized, locked up under control of relay R<10> and put relay R<13> under control of relay R<14>. If the wanted line is busy relay R<14> on relapsing connects busy tone to relay R<10> which functions as a transformer. Supply of ringing current. If the wanted line is idle relay R<12> energizes in series with relay R<22> at the called subscribers line switch, when relay R<14> relapses, short circuits part of its winding to mark the line busy and energizes relay R<15> which sends ringing current from the source S M to the wanted line and causes idle tone to be connected to relay R<10>. Reply energizes relay R<17> which locks up and releases ringing relay R<15> which completes the connection. Relay R" also is energized, cuts out relay R<13>, and grounds the cwire of the called subscriber. The called line is fed with current through relay R<11> and the bottom winding of relay R<12>. Release. When the calling subscriber hangs up relays R<1>, R<9>, R<10> fall back and relay R' releases relay R<3>, which releases relay R<7>. A circuit is thus completed from commutator C, through relay R<8> to the rotary magnet M<2> which restores the numerically operated wipers of the group selector to normal. When the called subscriber hangs up. relays R<11>, R<12> of the connector fall back and energize relay R<16> which locks up under control of the tens off-normal contact k<1>, completes a circuit including magnet M', off-normal contact k<2>, relay R<20> and commutator C<2> and another including magnet M<5>, relay R<19>, commutator C<2>, and the units off-normal springs k<1>. The resistance of relay R<20> is too high to allow magnet M<4> to be operated and relav R<19>, which though slow to release is quick to operate, breaks the circuit of relay R<20> before the latter has attracted its armature. The units wipers are therefore restored to normal whereupon relay R<19> falls back and allows relay R<20> to enter. gize. Relay R<20> short circuits part of its winding so that magnet M<4> operates and the tens wipers are restored. Relays R<16>, R<18> fall back and the latter releases relay R", the connection being now completely released. Thermostatic devices are provided for giving an alarm in case one of the parties fail to hang up.