Transistorized time multiplexer for telemetering

A transistorized time multiplexer or commutator is described with applications to telemetry. The unit develops a commutated PAM signal corresponding to the IRIG standard for time multiplexing of an fm/fm signal. The channel input impedance is 500 k ohms and the channel response is accurate to ±0.5 per cent of modulation range. The present unit includes 15 channels sampled 10 times per second, but channel switching rates up to at least 15 kc are feasible. Channel selection is achieved by two multivibrator rings operating a matrix of diode switches. The commutator consumes 1 watt from a single 45 volt supply, the accuracy being virtually unaffected by ±20 per cent change in supply voltage. The unit will operate satisfactorily with channel accuracy maintained at ±0.5 per cent and the commutating frequency changing less than 1 per cent in the temperature range 25°C. to 70°C.