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 PM-IM signal. The channel input Impedance is 500 k ohms and the channel re¬sponse is accurate to ±0-5$ 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 commentator consumes 1 watt from a single 45 volt supply, the accuracy being virtually unaffected by 20％ reduction in supply voltage. The unit will operate satisfactorily with channel accuracy maintained at ±0.5$ and the commutating frequency changing less than 1% in the temperature range 25 degrees C to 70 degrees C.
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