Patent GB-196300-A (GB)
Abstract: 196,300. Arter, R. C. April 17, 1922, [Convention date]. Automatic exchange systems; metering.-A pre-selected idle outgoing trunk is connected backwardly to a calling trunk by tens and units switching relays, individual to the outgoing trunk and controlled by tens and units control relays common to the group of incoming trunks to which the calling trunk belongs. The first set of impulses causes a temporarily used relay register to select an idle selector trunk in the desired group, a relay finder associated with this trunk then making connecting with the calling line. The call is similarly extended to a connector trunk, a relay register being operated by the tens impulses and then by the units impulses to select the wanted line. The call may be extended over a two-way inter-exchange trunk. Supervisory signals are given if certain control relays do not operate within a timed period, if all the connecting circuits are in use, or if the calling subscriber does not replace his receiver after a call. Special arrangements for calls to private branch exchanges, for supplying ringing-current, and for metering are described. Wrong connections due to the accidental transmission of an impulse by the hook-switch are avoided. Connection of calling line to idle connecting circuit, Figs. 2, 3, and 4. This is effected by tens and units relays 40, 50 under control of temporarily used tens and units control relays 10, 11, 12 - - -, 20, 21, 22 - - - common to the calling group. When subscriber A removes his receiver, line relay 1 connects non-dialling tone to line and energizes the appropriate tens control relay 11, which locks up and causes a relay 4 to isolate the other tens control relays, such as 10, 12. Relay 11 also energizes a relay 6, which connects up the units control relays 20, 21, 22, thereby energizing relay 21, which locks up and causes a relay 5 to isolate the other relays 20, 22, &c. The control relay 30 of the first idle connecting circuit is then energized over contacts of relays 31, 35, 6, 5 completing circuits for the appropriate tens and units relays 40, 50, which extend the calling line. Relay 30 also causes relay 32 to energize relay 43, Fig. 4, which energizes (1) relay 31 to extend the starting circuit to the next idle connecting circuit and disconnect relay 30, and (2) cut-off relay 2 to disconnect line relay 1 and the tens and units control relays. Relays 41, 45 energize over the calling line. If, due to faults, the connection is not made within a certain time, the call is extended to a second connecting circuit. A calling line, such as A<1>, Fig. 3, in another tens group normally has access to a second connecting circuit. Supervisory signals associated with relay line finder. A relay 9 having a vibrating armature is energized over contacts of relays 8, 5, 11 when a call is made. Relay 9 energizes relay 8, which locks up, disconnecting relay 9. During the vibration of the armature of relay 9, relay 7 remains energized. If the tens and units control relays do not operate properly, the relay 5 does not energize before relay 7 de-energizes, so that a circuit is closed for lamp 36 and supervisory relay 37. Similarly, if the relay 5 does not restore within a certain time, a similar indication is given under control of relay 7'. If all the connecting circuits are in use when a call is made, the circuit of relay 37 and lamp 36<1> is completed over the series contacts of relays 31, 31<1>, 32<1>, 31<1>, 32, 31 to ground at relay 11. This circuit also energizes a relay 33, which prevents the lighting of lamp 36. Similar supervisory circuits are associated with other relay selectors. Connection to idle trunk in wanted group of connectors. When the connecting circuit A, Fig. 4, is taken into use, relays 41, 45 energize over the calling line, and close a circuit for relay 51 which locks up. At the first selecting impulse. relay 52 is energized by relay 45, locks up, and prepares a circuit for relay 53, which energizes when the line circuit is closed and opens the looking circuit of relay 51. Successive line interruptions energize pairs of relays 54, 55; 56, 57; &c. the relays 55, 57 &c. opening the locking circuits of preceding relays. When the impulses cease, a slow-acting relay 42 energizes through an impedance 48 and closes a circuit over a contact of the last operated relay 55, say, for a relay 301, Fig. 8, in the desired hundreds group. The tens control relays 310, 311, 306 and the units control relays 320, 321 act like the relays 10, 11 and 20, 21, Fig. 2, to control the tens and units relays 340, 350 of an idle connector trunk which is thus extended to the calling line. The control relays then revert to common use. A supervisory lamp 49 lights up if the subscriber does not operate his dial, or if a fault occurs on a line. Preventing wrong connections due to accidental transmission of impulse by hook switch. If a single interruption only is sent, relays 52, 53 energize as described above, and the slow-acting relay 42 closes a circuit over the armature of relay 53 to energize a relay 44, which restores the relay register. Operation when subscriber dials a digit above the exchange capacity. The relay 57 corresponding to an unused digit, such as 3, has its outer contact connected to a relay 58, which is energized when the digit 3 is dialled and starts the tone generator to transmit a tone signal to the subscriber. Connection to called line. When the trunk C, Figs. 9 and 10, is taken into use, relay 345, Fig. 9, energizes over the calling loop, and relays 361, 362, 364, and 351 are also energized. The impulses of the tens digit operate pairs of the relays 352 - - 359, as before, and when the impulses cease, the slow-acting relay 342 closes a circuit for the tens control relay 465, Fig. 10, which connects the tens relays 470, 470<1>, &c. to the marking wires M, thus energizing relay 470, say, over the marking wire selected by the relay register. The tens relay 470 locks up and energizes a marginal slow-acting relay 407 to open the locking circuits of the register relays and of the tens control relay 465, and to start the ring- ing and busy-tone machine. The relay register is again operated by the units impulses, and when these cease, the slow-acting relay 342 closes a circuit for the units control relay 455 which connects the marking wires M to the units relays 460, 460<1> &c., thus energizing relay 460, say, over the selected marking wire. The relay 460 locks up and energizes a marginal relay 406 which restores the register relays and the units control relay 455. Busy test and signal. The test relay 405 is connected to the test lead of the wanted line during the release of a relav 430 energized in parallel with the units control relay 455. If the line is busy, relay 405 energizes, locks up, connects busy tone to the calling line, and closes a fresh circuit for relay 430 to keep the talking circuit open. Ringing-current. The relay 406 closes a circuit for a relay 423 having a vibrating armature which energizes slow-release relays 421, 422. As long as the armature of relay 423 intermittently engages its front contact, relay 421 energizes the ringing-relay 425 to connect up the generator 424. A ring-back signal is given by part of the ringing- current passing over the back contacts of relays 405, 420 to the calling line. The contacts of relay 423, and the relays 421, 422, are so adjusted that relay 422 de-energizes some time after relay 421, thus again energizing relay 423 to repeat the cycle of operations just described. When the subscriber replies, relay 410 permanently opens the circuit of the ringing-control relays 421, 422, 423. Relay 410 also energizes a relay 403, which closes fresh locking-circuits for relays 402, 460,. 470 and also energizes a self-locking relay 404. Release is controlled by the calling party, but the connector is not released until the called party also has hung up. When the calling party replaces his receiver, relays 41, Fig. 4, and 345, Fig. 9, de-energize. Relay 41 causes relay 43 to release relays 2, 31, 40, 50, and relay 345 causes the release of relays 362, 361, 350, 340, 44, and 404. When the called party hangs up, relay 410 causes relay 403 to open the locking circuits of relays 402, 460, 470. If the called party hangs up first, relays 410, 403 release, but the relays 460, 470 are locked to ground at relay 364. A supervisory lamp 401 lights up until the calling- party hangs up. If he delays unduly, an attendant can release the connection by operating key 401<1>. Private branch exchange lines, Figs. 10 and 11. One or more groups of P.B.X. lines are allotted to certain tens relays, such as 470', the appropriate units relay, such as 460<1>, being energized according to the line to be taken into use. If the first line of a group is called, connection is made to the first idle line of the group, but if any other line is called, connection is made to that line or a busy signal given Fig. 11 shows two branch exchanges, 590, 590<1>, each having three lines, associated with the tens relay 470<1>. A calling subscriber dials the tens digit to select the tens relay 470', relay 407 energizing as before. Assuming the units digit of the first P.B.X. line to be 3, the subscriber energizes the relays 356, 357 of the connector register. At the end of the units impulses, the slow-acting relay 342 closes a circuit which includes the front contact of relay 407, and contacts of relays 470<1>, 505. to energize relays 506, 509 of the P.B.X. control relays. Relay 509 energizes relay 505 to prevent the control relays being taken into use for another call. Relay 506 causes relays 510, 515, 520- to energize in succession. A circuit is now closed from the outer armature of relay 342,. Fig. 9, over contacts of the register relay 357, of P.B.X. control relays 510, 520, of the cut-off relay 502<a> of the first P.B.X. line and (if this is idle) o