GB622968A - Improvements in and relating to two-way carrier signalling - Google Patents

Abstract

622,968. Carrier transmission. GENERAL ELECTRIC CO., Ltd., and LEY, D. A. Jan. 24, 1947, No. 2273. [Class 40 (iv)] In a two-way system having a wideband channel for the transmission of music &c. and employing singlestage modulation and demodulation in one direction and doublestage modulation and demodulation in the opposite direction, the single-stage modulator and demodulator are reversible and serve respectively as the second stage demodulator and first-stage modulator for the twostage direction. A standard multi-channel system is shown working on 8-10.4 kc/s., 11.2-13.6 kc/s. and 14.6-17 kc/s. in one direction and 20.1-22.5 kc/s., 24-26.4 kc/s. and 28-30.4 kc/s., F8 and 9 and F16 and 17 being the directional filters covering the whole range in each direction respectively, and two contiguous channels may be taken over for the wideband transmission by operation of switches S1-4, the switches S5-9 being as shown for transmission from station A to station B and in the alternative position for transmission from B to A. A 0-5.6 kc/s. signal applied to the input terminal T1 is fed via switch S5 and filter F21 to the modulator M1 and modulates an 8 kc/s. carrier. The upper sideband selected by the filter F22 is passed via switches S6 and S1, amplifier MA3 and filters F8 and F3 to line L. At station B the signal passes via filters F4 and F9, amplifier MA4, switches S3 and S7 and the 8-13 kc/s. channel filter to the demodulator DM2 from which the 0-5.6 kc/s. signal output is selected by the filter F26 and amplified by MA2 before passing via switch S9 to the output terminals T3. With the switches S5-9 in the alternative position, a 0-5.6 kc/s. signal applied to the terminals T4 passes via switch S8 and filter F26 to DM2, which, being reversible, delivers after sideband selection by the filter F25 an 8-13.6 kc/s. signal to the amplifier MA3 via switch S7. The signal is then passed to the second modulator and sideband selector M2 and F24 via the switch S9 and attenuating network AU producing a 20-26.4 kc/s. signal which is passed to line via switch S4, amplifier MA5 and filters F16 and F4. At station A the signal passes via the carrier filter F3, the directional filter F17, the amplifier MA6, the switch S2 and the wideband channel filter F23 to the first-stage demodulator DM1 and then via switch S6 to filter F22 which selects the 8-13.6 kc/s. sideband for demodulation in M1. The 0-5.6 kc/s. output from M1 is selected by F21 and passes via switch S5 and amplifier MA1 to the output terminals T2.