GB833933A - Improvements in or relating to an arrangement for effecting a selective connection between a pair of lines - Google Patents

Abstract

833,933. Automatic exchange systems. TELEFONAKTIEBOLAGET L. M. ERICSSON. Dec. 17, 1957 [Dec. 20, 1956], No. 39214/57. Class 40 (4). In order to effect a connection between a pair of lines each of which may be either a 2-wire line or a 4-wire line, each of the lines of that type of which there are fewer, say each of the 4-wire lines, is fitted with a hybrid transformer connected so as to present to the selector a termination of the other type, say 2-wire, and if two lines of the same type, which are both fitted with hybrids, are connected together, the operation of relays, which takes place as a result of the connection switches out the hybrid transformers. Assuming there to be fewer 4-wire lines than 2-wire, each incoming 4-wire line is equipped as shown on the left-hand side of Fig. 1, and each outgoing 4-wire line as shown on the right-hand side thereof. If such an incoming 4-wire line is connected to an outgoing 2-wire line, or if a 2-wire incoming line is connected to such an outgoing 4-wire line, the hybrid transformer in the 4-wire remains in circuit. If, however, two such 4-wire lines are connected together the relays 1, 1<1> pull up in series over. the fourth wire b2 of the link, and operate the relays 3, 3<1> which remove the respective hybrid transformers from the circuit, thus providing a direct 4-wire to 4-wire connection. An arrangement is described with reference to Fig. 2 (not shown) in which each 2-wire line is provided with a hybrid transformer, the 4-wire lines being then without hybrids.