GB381232A - Improvements in or relating to two-way signalling systems comprising electrically long transmission lines - Google Patents

Abstract

381,232. Two - way transmission. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.- (Assignees of Bjornson, B. G. ; 57, Horatio Street, New York, U.S.A.) July 3,1931, No. 19268. Convention date, July 9, 1930. [Class 40 (iv).] In a two-way submarine cable system in which a speaker in one direction gets complete control of the system so that speech in the other direction can only normally take place after a pause in the first speech equal to at least the transmission time over the cable (T), the control circuits are so modified after a predetermined time that the distant listener is able to break in and obtain complete control during a slight pause which may only be that normally occurring between words. In the system shown, when speech arrives over land line TL, relays 7, 8 transmit a courier control pulse over the cable TC, network 1 delaying the speech for a short time (t) sufficient for the control operations to be completed. At the distant station the courier pulse passing through filter 23 operates relays 27, 28, 29 for conditioning the transmitting and receiving branches, relay 30 for disconnecting relay 16, and relay 26 for connecting up speech filter 24 whereby the speech takes over the control initiated by the courier. At about the same instant at the transmitting station, part of the courier pulse which has been delayed for time T-t in network 14 passes into circuit 13 operating relay 16 to prevent any change of condition by received speech. After a further period T produced by network 18 control device 19 operates energizing relay 20 which disconnects circuit 13 so that the control of relay 16 now takes place over its left-hand winding by speech passing through delay circuits 14, 18. At a slight pause in the received speech, during the period between the release of relays 30, 31, the distant listener can break in, operating relay 16 immediately over its right-hand winding and sending a courier pulse back to the transmitting end at which the arrival of the courier will synchronize with the release of relay 16 so that both stations are now conditioned for speech in the opposite direction. Specification 338,971, [Class 40 (iv), Telephones &c.], is referred to.