Abstract: An improved precipitator voltage control system including an automatic voltage control (AVC) circuit, a firing circuit, an alarm circuit, a power-saving circuit, a remote set-point control circuit and a power supply, all of which are mounted on a single, readily interchangeable circuit board. The automatic voltage control circuit includes a highly responsive spark detection subcircuit which causes the transformer/rectifier voltage to be reduced to zero at the end of the half-cycle in which a spark occurs and then causes the voltage to remain at zero for a short period of time after which voltage is reapplied in a dual ramp manner causing it to rapidly reach a level below the precipitator arcing potential and then increase at a slower rate to the threshold of sparking. The firing circuit drives silicon-controlled rectifiers (SCRs) through optical couplers which provide several thousand volts of circuit isolation.

Abstract: A multi-function LED wristwatch in which all the required functions may be performed with the use of only two push button switches. These switches are time demand for displaying hours, minutes and seconds and date demand for alternatively displaying day of month, month of year, AM or PM of time, and day of week. They also perform all the setting functions for these displays and through sequential button depression and digital logic circuits, five of the functions, namely hours, minutes, day of the month, month of the year, and day of the week may be set independently.