Burner control system with secondary safety switch

A burner control circuit responsive to a thermostat comprising:

• a primary circuit connected across a line voltage including:
• an electronic switch for connecting a burner motor to the line voltage, a circuit breaker switch, a light responsive element for a first optical coupler, and a light generating source for a second optical coupler;
• and
• a secondary circuit including:
• a flame detecting cell, a light source for said first optical coupler operatively responsive to the thermostat, a light responsive element for said second optical coupler, a current sensitive element operatively connected to said circuit breaking switch, and an electronic switch operatively connected to the thermostat, said flame detecting cell and said light responsive element of said second optical coupler for admitting current to said current sensitive element.

A transistor circuit comprising:

• a first source of current;
• a second source of current;
• an asymmetrical diode responsive to said first source wherein said diode will conduct current in response to a current applied by said first source;
• a PNP transistor having its emitter connected to said second source and its base connected to said diode, effective to maintain said diode in a current conducting state and therefore said transistor in a current conducting state after said first source has been switched off.