Reduced arcing contact switching circuit

DETAILED DESCRIPTION What is claimed is: 1.
Where alternating current is applied to a load through electrical contacts, a contact-switching circuit for opening and closing the electrical contacts at a predetermined phase angle of the alternating current signal, comprising: means for providing the alternating current signal; first means responsive to said alternating current signal for producing a count signal that represents successive phase angles of said alternating current signal; means for providing a selectable fixed timeslot count representing the alternating current phase angle at which movement of the electrical contacts must be initiated so that the contacts will reach their desired position at a predetermined phase angle; comparator means for comparing said count signal and said fixed timeslot count and for producing an enable signal when there is a predetermined relationship therebetween; means for providing a control signal; and means for controlling the electrical contacts in response to said control signal when enabled by said enable signal.
2.
The contact-switching circuit of claim 1 wherein the first means includes: an oscillator synchronized to the alternating current signal for producing an oscillating signal having a frequency that is approximately a multiple of the alternating current frequency; and a counter responsive to said oscillating signal for producing the count signal in response thereto.
3.
The contact-switching circuit of claim 2 wherein the counter increments one count for each cycle of the oscillating signal.
4.
The contact-switching circuit of claim 2 including synchronization means disposed so as to be responsive to the alternating current signal for producing a synchronization signal that is input to the oscillator for synchronizing the oscillator to the alternating current signal.
5.
The contact-switching circuit of claim 2 including synchronization means disposed so as to be responsive to the alternating current signal for producing a synchronization signal that is input to the counter for synchronizing the counting action of the counter to the alternating current signal