Patent ID: 7543170

Claim:
A safety circuit for monitoring and controlling power to an equipment operated by a computer executing control software to cause said equipment to “fail safe” in the event of a safety alert, said safety circuit comprising: a detector circuit for receiving an alternating state telemetry signal from said computer, wherein said alternating state telemetry signal indicates a satisfactory operation of said computer and said control software; a relay circuit for applying power to said equipment; a first counter, coupled to said detector circuit, for outputting a first alert signal to said first relay circuit in response to an interruption in said alternating state telemetry signal received by said detector circuit; a second counter for outputting a reset signal to cancel said first alert signal in response to a resumption of said alternating state telemetry signal being received by said detector circuit in less than a predetermined timeout period after said interruption, thereby preventing said safety circuit from removing power from said equipment; and a switching circuit, coupled to said detector circuit, for switching said relay circuit to remove power from said equipment in response to said interruption lasted longer than said predetermined timeout interval.