GB405026A - Carrier current transmission system - Google Patents

Abstract

405,026. Wired wireless signalling; impedance networks. STANDARD TELEPHONES & CABLES, Ltd., Connaught House, Aldwych, London.-(Assignees of Weis, C. L. ; 4905, 39th Avenue, Long Island City, New York, U.S.A.) July 29, 1932, No. 21416. Convention date, Aug. 14, 1931. [Classes 40 (iii) and 40 (v.] A carrier current system transmitting a wide band of frequencies comprises a plurality of channels arranged in groups so disposed in the frequency spectrum that those in one group lie between those in another group. In the system described low frequency lines l1, l2 &c., Fig. 1, are divided into groups A-R each containing for example sixty lines, and each of which passes to a modulator M fed from generators G1-G60 with intermediate frequencies ranging from say 263 KC to 499 KC. and separated by 4 KC. The lower sideband is selected by band filters CBF1-CBF60 the output from the odd filters being taken to a valve amplifier A1 and that from the even filters to an amplifier A2 both amplifiers feeding a line individual to the group such as L1 for group A, L2 for group B and so on. The amplifiers A1, A2 may be replaced by resistance pads 7, 8, Fig. 3, the input circuits 9, 10 and the common output circuit 19 being arranged as shown or by a hybrid coil 21-24, Fig. 4, arranged as shown. The total output from each of the groups A-R is dealt with in a manner similar to that from each line l1, l2, &c., passing to modulators M<1> fed from generators C1-C18 with radio frequencies ranging from say 1080 KC. to 5160 KC., and separated by 240 KC. The outputs from the modulators pass to band filters GBF1-GBF18 the output from the odd filters being taken to an amplifier A3 and that from the even filters to an amplifier A4 both amplifiers feeding a further amplifier A5 connected to the outgoing line LE which is preferably of the coaxial conductor type. The receiver circuits are also described (Fig. 2, not shown) and comprise a similar arrangement of apparatus to the transmitter, the amplifiers operating in the reverse direction and the modulatiors being replaced by demodulators and curves are given (Figs. 5 and 6, not shown) showing the impedance-frequency characteristics of the band filters CBF and GBF. Specifications 130,432, 131,426, and 142,115, [all in Class 40 (v), Wireless signalling &c.], are referred to.