The only external power source on the range I bought used is a single AA battery
. It connects through a momentary on switch to a box with two terminals on the bottom (one from the (-) of the battery
and the other from the (+) via the switch.
On top of the box are six more terminals. One is not used. Three connect to lighters for the top burners, one to the lower oven burner and the fifth to the upper broil burner. I opened the box. It looks like a multivibrator circuit driving a step-up transformer. With a good battery
you get a series of sparks at each burner when you push the button.
Each burner also has a thermocouple. These output about 25 mv when heated. When you turn on the burner gas you push in on the knob and hold it in while turning it to the high flame position. You also hit the lighter switch which lights
What happens is inside the valve, as the knob is pushed in, propane
pressure sets a spring loaded plunger against an electromagnet. As you continue holding in the knob the burning propane
heats the thermocouple. At some point there is enough thermocouple current applied to the electromagnet to hold the plunger in position, and you can let go of the knob and do your cooking. However if the flame goes out, the thermocouple cools and stops generating enough current to hold the plunger. It springs away from the electromagnet and shuts off the gas to that burner.
The reason I know this is because the oven burner wouldn't stay lit. I suspected the thermocouple or electromagnet/plunger was bad. So I took it all apart. I had a need to go to Seattle anyway so bought a new thermocouple and plunger valve from Sure Marine. It turned out I didn't need the new parts, the jet to that burner was just partially plugged. It all works fine now and I have the parts tie-wrapped underneath in case I ever actually need them.
So it appears that Force 10 has figured out a way to provide this safety feature without any external power.