GB393288A - Improvements in or relating to telegraph systems - Google Patents

Abstract

393,288. Telegraph systems. AUTOMATIC ELECTRIC CO:, Ltd., Strowger Works,' Liverpool. Nov. 30, 1931, No. 33189. Convention date, Nov. 28, 1930. [Class 40 (iii).] A repeater forming part of a reactance-less circuit comprises thermionic valves and electromagnetic relays so arranged that signals repeated to the outgoing line do not disturb the incoming line. When the normally closed line 1, Fig. 1, is interrupted by a distant transmitter, valve 3 ceases to pass current. Sending-on contact 5b opens and passes on the signal to line 2. In order to prevent consequential interruption at 10b of the sending line 1, a holding-winding 10<1> is provided ; when relay 5 releases owing to the stoppage of valve 3, contact 5a opens and unshort. circuits this winding, which then holds contacts 10a, 10b during spacing, while winding 10 holds them during marks. Break-in signals and call-acknowledgments are effected by interruption of line 2 at the receiving station. This ensures that line 1 shall be broken at 10b when closed at its own transmitter. Transmission from line 2 to line 1 is similarly effected. In a modification. Fig. 2, holding-valves 27, 28 are employed instead of the holding-windings 51, 101. A spacing interruption of line 1 paralyzes repeating-valve 3 and opens contact 5b to send on the signal to line 2 as described above. At the same time by opening contact 5a it renders holding-valve 28 operative so that relay 10 is held-on and line 1 therefore remains closed at 10b while holding-valve 27 remains paralyzed through 10a. When the receiving operator interrupts line 2 to send a break-in signal or acknowledge a call, he paralyzes valve 4 so that when line 1 is sending a marking signal so as to paralyze the holding valve 28 through contact 5a, relay 10 releases and breaks line 1 at 10b to disable the sounder on line 1. In a modification, Fig. 3 (not shown), a single valve serves as repeating valve 3 and holding valve 27, and similarly a single valve replaces valves 4, 28, the opening of contact 5a in the case unshort-circuits a source of positive biassing potential so as to hold valve 4 in the operative state. The coils 16, 22 may be replaced by resistances, Fig. 4 (part not shown). Station circuits. A party-line system may comprise stations arranged as in Fig. 4, where the only impedances in the lime are the resistances 106, 106 and the resistance (corresponding to 16, Fig. 1) at the repeater station (not shown) on line 1. Current is normally flowing when the line is idle. The sending station opens its switch 151 to unshort-circuit its key 105, and the latter, by controlling the potential drop in resistances 106 operates the sounders 114 through valves 107 and relays 112.