Low-Speed Time-Multiplexing with Magnetic Latching Relays

Many satellite and spacecraft telemetry systems require that measurements be time-shared at relatively low rates (less than one sample per second) and that several rates be available in order to minimize redundant sampling. This paper discusses a multiplexing system designed specifically for low-speed operation and multiple-rate flexibility so as to gain advantage in other critical areas of performance. A unique synthesis of the basic circuit provides for the time-multplexing of n measurements with n-1 magnetic latching relays. Assuming an external two-phase clocking source, no other components, active of passive, are required in the circuit. Other advantages of the circuit are: 1) low average power consumption, 2) no additional monitoring or reset circuitry required to insure proper operation at turn-on or after momentary power failure, and 3) the virtual impossibility of switching more than a single measurement to the common output line, even in the case of component or wiring failure.