I've got one of those too and was wondering about that. Mine has a switch on the wall but I haven't checked to see what the power is. I'm thinking it's a 120v solenoid valve.
Most of them have a 24 V transformer to run a thermostat and a gas valve. Several have a millivolt system that will run the burner without the fan using voltage from the pilot generator. There could be a rocker switch under the control cover that says on, off, thermostat. On T/stat it functions through the stat, on gives you manual control and constant on. 120 V on a gas appliance is rare for the control system and thermostat circuit.