GB1384971A - Signal switching arrangement - Google Patents

Abstract

1384971 Signal switching circuits; RF and IF band circuits NIPPON TELEGRAPH & TELEPHONE PUBLIC CORP and NIPPON ELECTRIC CO Ltd 15 Jan 1973 [14 Jan 1972] 1921/73 Headings H3W H3Q and H3P In a signal switching arrangement for selectively connecting one of first and second input terminals A, B, Fig. 1b, to a signal output terminal C comprising a plurality of electromagnetic relays RL1-RL4 having a common operating circuit for their operating coils BL1-RL4 and whose contacts r11-r14 connect the first and second input terminals to the output terminal in first and second states of the relays, each operating coil is connected in series with a corresponding first variable impedance RV1-RV4 and in parallel with a corresponding second variable impedance RV5-RV8 so that the response time of each relay to a change in current in the operating circuit may be adjusted so that during switching the signal output terminal is always connected to at least one signal input terminal. The signal switching arrangement may be used for the radio frequency band circuit and/or intermediate frequency band circuit of a microwave communication system. The response times of the relays RL1-RL4 to energization are controlled by adjusting the variable resistors RV1-RV4 and the response of the relays to release are controlled by resistors RV5-RV8. The relays may be single pole double throw break-beforemake type connected as in Fig. 1b. Assuming the input signal at A is connected via contacts rl1 and rl2 to C, by suitable adjustment of these resistors when the switch S is closed the contacts rl4 and rl3 are first closed to connect the input signal at B also to C as the contacts rl2 and rll are opened to disconnect the signal path between A and C. The same principle is applied for setting the response time of the relays for the disconnection of the power supply as is perfomed in order to restore the state of the signal after switchover. Signal overlap switching can be obtained by adjusting the variable resistors. However increased signal level at the output C then occurs when the two input signals A, B of identical phase occur simultaneously at the output C during the switching operation. In order to avoid this a mercury relay of the bridge, i.e. make-before-break type, is used as e.g. relay RL1 and the response time of the relays to the energization are suitably controlled (Fig. 7, not shown), so as to provide in an equivalent circuit (Fig. 8, not shown), in which level variation of the signal applied to the load (R 0 ) is avoided. The operation of the mercury relay moveable contact in relation to two fixed contacts is disclosed (Figs. 9a-9c, not shown).