Patent GB-677421-A (GB)
Title: Telegraph exchange system
Inventor: OBERMAN ROELOF MAARTEN MARIE
IPC: H04L12/00
Filed: 1947-12-30
Abstract: 677,421. Telegraph exchange systems. STAATSBEDRIF DER POSTERIJEN, TELEGRAFIE EN TELEFONIE. Dec. 30, 1947 [Sept. 2, 1943], No. 34840/47. Class 40 (iii). In a telegraph exchange system having repeaters at the exchange to establish connections between lines of different natures, such as two-wire single-current lines, four-wire singlecurrent lines and four-wire double-current lines, the repeater is provided with discriminating relays both at the incoming end (to which calling subscriber's lines become connected) and at the outgoing end (to which called subscriber's lines become connected), said relays being presented by the means by which said calling or called lines become connected to said incoming or outgoing ends respectively, to the exchange terminals of the lines and said discriminating relays either not operating or operating in a particular manner determined by the nature of the connected line for adapting the repeater to the nature of the connected line. On the initiation of a call from a 2-wire single current subscriber, such as es2, a line-finder such as OZ connects the repeater to the calling line and a further finder, such as KZ, connects a free register with the calling line as described in Specification 658,514. In the normal condition of the repeater, current from positive battery at the exchange passes through the right-hand winding of relay A and contact a1 is in the position opposite to that shown. When a free register is found, relay KB operates and at contact kb1 current passes over lines 1, 2 and through the windings, in series, of relay A so that contact al is moved to the position shown allowing relay LA to operate. At contact la2 relay DA operates and at contact da2 positive voltage from wiper c of the register connector KZ is applied to the junction of the two windings of relay A. The selecting impulses actuate relay A and control relay O of the register. When the called line is found, relays KC (not shown) and KD operate and relays LB, DB, Fig. 2, operate, the relay B being operated to move its armature b1 to the position shown. Signals from a station es2 are repeated by armature a1 over contact kd2 and db2 to the junction of the windings of relay B and over contact eb2, contact kc1 and the wiper a of the final selector FS leading to the called subscriber. If a 4-wire single-current subscriber es4 is to be connected to another es4 subscriber the calling subscriber connects two lines 3-4 when the called subscriber has been found and relay CA operates, effecting the release of relay DA so that positive potential is applied over contacts ea4, da2 to the junction of the windings of relay A. Signals from the calling subscriber operate relay A which at contact a<SP>1</SP> repeats the signals over contacts kd2, db1, lb1, kc2 and wiper b to the lines 3, 4. The called subscriber controls relay B and its contact b1 passes signals over a circuit comprising contact kd1, released contact da1, contacts la1, kb2, wiper b of switch OZ and lines 3, 4 of the calling subscriber. In the connection of a four-wire doublecurrent subscriber ds4 to a similar subscriber, relay KB operates kb1, kb2 and as the left-hand winding of the relay A remains unenergized, relay A does not operate. Contact a1 remains in the position opposite to that shown and relay LA does not operate. Relay EA operates over a circuit from negative battery, released contact la1, contact kb2 to relay ZR at the calling station ds4. At contact ea3 relay CA is shortcircuited and at contact ea5 a holding circuit is prepared for relay EA and the circuit of relay DA is opened. Contact ea4 removes positive voltage from the junction of the windings of relay A and contacts ea1, ea2 are switched over so that relay A operates. Relay LA is now operated and connects positive voltage from contact or of relay ZR to the register relay O so that the subscriber ds4 can control the register. When the connection to the called subscriber has been established, relays KC (not shown) and KD operate and subsequently relays B, EB, LB are energized. The signals from the calling station are repeated by armature a1, contacts kd2, db1, resistance x2, contacts lb1, kc2 and line 3 to relay ZB. The signals from the called station pass over line 1 to wiper a, contact kc1, operated contacts eb1, eb2 and resistance x1 and are repeated by contact b1 to contact kd1, released contact dal, operated contacts ea3, la1, kb2 to line 3 and relay ZR at the transmitting station.