Patent ID: 7286333

Claim:
An apparatus comprising: an arming and firing circuit for applying a control voltage to a load, the arming and firing circuit comprising: a first portion including a first switch configured to be coupled to a first voltage; a second portion operatively coupled to the first portion and including a second switch; and a third portion operatively coupled to the second portion and configured to be coupled to the load, the third portion including a third switch; wherein the first portion is configured to receive a first input signal and to activate the first switch in response to a first value of the first input signal to couple the first voltage to the second portion; wherein the second portion is configured to receive a second input signal and to activate the second switch in response to a second value of the second input signal and in response to the first voltage from the first portion to couple a second voltage to the third portion; wherein the third portion is configured to receive a third input signal and to activate the third switch in response to a third value of the third input signal and in response to the second voltage from the second portion to couple the control voltage to the load; and wherein the first portion includes: an optocoupler coupled to receive the first input signal and configured to output a low signal in response to the first value of the first input signal; a first transistor coupled to the optocoupler and configured to shut off in response to the low signal from the optocoupler; a second transistor coupled to the first transistor and configured to turn on in response to the shut off of the first transistor; and third and fourth transistors coupled in parallel and coupled to the second transistor, the third and fourth transistors being further coupled between the first voltage and the second portion and being configured to turn on in response to the second transistor turning on, thereby coupling the first voltage to the second portion.