GB153563A - Repeaters for multiplex signalling systems - Google Patents

Abstract

153,563. Western Electric Co., (Assignees of Kendall, B. W.). Oct. 31, 1919, [Convention date]. Multiplex systems; thermionic relays.-Carrier currents of different frequencies, separately modulated for the multiplex transmission of speech &c. are repeated by a single amplifier, which is designed to have a substantially rectilinear characteristic so as to avoid cross-modulation. In the two-way repeater shown at the right of the Figure, each amplifier consists of a pair of thermionic valves having their grids connected to the two ends of the input transformer coil 29, so as to be oppositely affected, .and with their anodes connected through inductances 38, 39 and a supply battery 35 to the mid-point of the same coil. The terminal station shown at the left of the figure comprises transmitters T<1>, T<2> and receivers R<1>, R<2> connected to a balanced transformer 7, 8, 9 between the line 1, 2 and artificial line 5. Each transmitter comprises a carrier-current generator 10 and a microphone circuit 12, both coupled to a modulating-valve 11, the output circuit of which is connected to the coil 9 through circuits 21, 22 tuned to the carrier frequency. A filter F prevents currents of audible frequencies from passing to line. At the repeater station, the currents pass from the mid-points of a transformer 26, 27 (balanced with respect to the line 1, 2 and artificial line 6) to the input transformer 28. 29, and the amplified currents pass through condensers 40, 41 and transformers 42, 43, 44 to the line 3, 4. Currents in the reverse direction are repeated by the lower amplifier to the line 1, 2 and are sorted into different receiving-channels R', R<2> by tuned circuits such as 49, 51. The speech-modulations are detected by valves such as 52 and transmitted to receivers such as 53 through filters which prevent the passage of currents of the carrier frequency. The line 1, 2 may also carry ordinary speech currents.