> > Thermocouple wire going to a comparator. Simple, cheap, and dead

reliable.

This is more or less the fire loop used in commercial aircraft

engines.

Mike Harrington

Seems there was an article in kitplanes many moons ago describing fire
detectors that used a low melting point metal. the metal melts, circuit
opens, the big red light comes on. This has the advantage of letting you
know if the circuit goes bad.

Monty

Mark Wrathall wrote:
The fire loops used on commercial turbines are made up with a cross section
like coax cable. The shield and core are solid metal, separated by a low
melting point salt which insulates as a solid. When melted, it conducts,
shorting the two conductors, and turning on the light in the cockpit
(basically).

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