Abstract: A control arrangement for a fuel ignition system to provide an interlock on start-up to prevent energization of fuel valves under certain failure conditions includes a pulse generating circuit operable when enabled to provide pulses for enabling a first switching device which energizes a pilot valve to supply fuel to a fuel outlet and prepares an energizing path for a main valve, and a second switching device enabled by a flame sensing circuit when a flame is established at the outlet to close associated contacts to complete the energizing path for the main valve and to cause the pulse generating circuit to continue to generate pulses for maintaining the first switching device enabled, the pulse generating circuit being inhibited whenever the contacts are closed at start-up, or close after the system is in a lock out state, preventing the enabling of the first switching device to maintain the pilot valve and the main valve deenergized.

Abstract: A thermal responsive switch employs a gas expansion operating member movable by changes in pressure of a gas charge in a chamber containing a carbonaceous adsorbent material formed from a compound of carbon and non-carbon component by removing the non-carbon component.