Abstract: A power monitor for providing a low impedance path to ground for a digital electronic system under certain circumstances dependent upon the status of the A.C. energization has a normally closed semiconductor switch coupled between the digital electronics system and ground. A bias voltage derived from the regulated D.C. power supply is delayed and applied to the switch to open it a predetermined interval after the A.C. is turned on. The bias is removed from the switch when the A.C. power is turned off prior to the time the regulated D.C. outputs deviate substantially from their nominal values.

Abstract: A two-wire voltage to current converter and transmitter for extremely high output impedance transducers has an input which floats with respect to the power supply ground potential and is referenced to the power supply ground potential by means of a level shifting comparator.

Abstract: A process control system including a control station responds to the departure of a process variable from a set point to provide a direct current signal in a two-wire transmission line in a direction dependent upon the direction of such departure and time-proportioned in accordance with the magnitude of the departure. A solid state power relay that accepts the d-c signal at a single pair of input terminals includes high-current rating triacs that are adapted selectively to be fired by triggering pulses generated in response to the d-c signals alternating current power from a source of alternating current to a heavy-duty motorized valve for operation of the latter in one direction or the other and at a speed in accordance with the signals.