GB323090A - Improvements in and relating to telephone systems - Google Patents

Abstract

323,090. Burnovox, Ltd., and Haynes, J. K. Nov. 15, 1928. Direct call systems.-In intercommunication systems having a pair of groups of lines running between all stations, the selecting switch at each station has two sets of contacts, the associated arms being connected respectively with the microphone and receiver, so that the microphone at the calling station may be connected in series with the receiver at the called station over a line wire in one group, the other microphone and receiver being connected in series over a line wire in the other group. Two systems are described, the first secret, and the second having conference facilities, and in the first system one particular station is limited to communication with one other station only. First system, Fig. 1. The home wires in each group a, b, are connected respectively to the switch-hook i and calling key q, and each station may be provided with loud-speaking and ordinary receivers p, o one or other of which may be connected up by a switch n. To call station 3, the selecting switch e, f of station 1 is placed on contacts 3, and ringing key q operated to complete a circuit over line b3 for the receiver o or p at station 1 and bell j at station 3 in series, ringing current being supplied by battery m. Ring-back tone is heard at station 1. The called party rotates his selecting switch until he hears a click, the receiver at station 1 having previously been taken off its hook. When the receiver at the station 3 has been removed and the ringing key at station 1 restored, independent circuits, fed by the batteries g, are completed for the microphone h at one station in series with the receiver at the other station, each circuit comprising a home wire in one group and a line wire in the other group. Station 4 has no call bell and can communicate with station 1 only, station 4 being called over its load-speaker p. Second system, Fig. 2. The circuits of Fig. 1 are modified for using a common ringing and speaking battery G, and each station is provided with a master switch s, t for connecting the microphone and receiver o or p to the switch arms e, f, the instruments being normally connected to the home lines. If the party at station 1 lifts his receiver off hook i, rotates switch e, f to contacts 3, and throws s, t, the speaking circuit from station 1 to station 3 is completed and the party at station 3 may be called over his loud-speaker. He may also be rung by pressing key q at station 1. The party at station 3 lifts his receiver to complete the speaking circuit from 3 to 1, operation of switch e, f at 3 being unnecessary. The party at another station can, in a similar manner, establish parallel circuits to station 3. The main control switch s, t may be locked in the operative position by a catch on the switch hook i, and may be connected to ringing key q so that normal operation of s, t does not operate q which however may be operated by a slight further movement of s, t.