Patent GB-320706-A (GB)
Title: Improvements in telephone exchange systems
IPC: H04Q3/00
Filed: 1928-08-04
Abstract: 320,706. Relay Automatic Telephone Co., Ltd., and Johnson, B. B. Aug. 4, 1928. Automatic exchange systems.-In a system such as that described in Specification 212,682, in which a register-marker is seized by a junction from a satellite and in response to digits denoting a local call sends back a signal to cause the junction to be released &c., the register-marker records the first 2 digits (or groups of digits) of the calling satellite and in response to the first digit (or group) dialled causes the call to be extended to a numerical division or, as described in Specification 309,711, to the common outgoing division, where a further register-marker is seized. If the 1st digit (or group) is the same as that of the calling satellite, the register-marker remains associated with the connection and responds to the 2nd, and if this indicates a local call causes the release of the connection so far established in the main office and the transmission of a signal to the satellite to cause the release of the junction &c. Selecting junction. A calling subscriber is extended in known manner to an A and B feed, Figs. 4 - - 6 and up, in which relays T4, AB4, G4, GX4 pull up, the latter releasing T4. Each bundle of outgoing trunks has a relay JMC19, JMC29, &c. for marking the group of outgoing junctions to be used and each local registermarker has a relay MC19 energized while it is marking. Provided all the relays JMC, MC are de-energized, FM19 pulls up, locks itself and energizes JMC19 which locks up, disconnects the other relays JMC and the relays FM, MC, energizes JM117, Fig. 17, associated with the junctions that are 1st choice to this group of outgoing trunks and marks the calling trunk by energizing OTM110, Fig. 10. OTM110 energizes the relays OTLM110 &c. of idle links and these over circuits such as ma1, Figs. 10, 15, 16, energize the relay GS117, which locks up, disconnects the subsequent GS relays and energizes OJM117, assuming both of the junctions shown are idle, to seize and mark the upper junction, and SS16 to energize the relays OJLM116 &c. of idle links. A circuit is now completed for the connecting relays of an idle route, viz., in the case assumed, OT110/OTL110, OTL115/- OJL115, OJL117/OJ117 and these lock up as usual in series with the respectively busying relays and relay RCO6 which releases FM19, JMC19. Connecting incoming repeater, Fig. 18, to register-marker, Figs. 20 - - 21. AB18 pulls up over both wires of the junction in parallel and is followed by G18, BB18 and FI119, the latter locking up over the a and b wires in parallel and energizing RC119 or RC219 to seize a register-marker. The latter is provided with 2 groups of relays PX, P for recording the 1st 2 digits of the satellite from which the junction comes. In the case of the junction shown these digits are 8, 2 and accordingly the contacts of RC119, RC219 are so connected that PX820 and P220 are operated. P220 prepares the registermarker in the usual way. Extension of call to numerical or junction division. The register-marker responds to the 1st digit or, if this is 7, the first two digits and marks out a connection in the required direction in known manner, RH20 being energized by the relay 1D that is operated at the end of the digit (or digits) and energizing the marking control relay MC20. If the digit is not 8, RH20 is energized over v or over z, PX820 - - 5 and its lower winding and the extension of the connection and consequently causes energization of RC0119 and releases the register-marker. If however the 1st digit is 8, RH20 is energized over its upper winding, PX8720 -- 4, and the wire y and energizes BYH20 which locks up and holds BY20 and RC119 in spite of the operation of RC0119. It also holds P220 after the relapse of PX820 which is released by RC0119. On the relapse of PX820, DM21 falls and DMJ22 pulls up. The register-marker then receives the 2nd digit at the end of which DC21 pulls up as usual and, if the digit is not 2, completes a circuit over s, h1 to short circuit RC119 to free the recorder. If the digit is 2, a circuit is made instead over n, yrs for JRS18 in the repeater. Release of main office connection and junction and establishment of local connection. JRS18 locks up, opens circuit h to free the registermarker and release the connection ahead, connects battery over AA18 to the a-wire in place of ground over AB18 which remains connected to the b-wire. IS5 in the A and B feed is thus unbalanced and energizes ICO5 which locks, extends the a-wire back to BA5, releases IS5 and holds RC06 and the connection to the junction independently of JR5 which is energized by BA5, and energizes RG6. RG6 locks up and releases ICO5 which releases RCO6 and the connection to the junction, whereupon BA5 and JR5 fall back and a circuit is made over RG6 - - 5 to initiate in known manner the seizure of an idle register-marker. In a modification in which the number of outgoing junctions is the same as the number of links OJL, the links OJL are connected directly to the junctions, h116 is grounded through a resistance, the points gs117, gs217 are bridged and contacts 4 of the relays GS are omitted.