>Its power source is an internal hermetically sealed capsule containing a mixture of gaseous and liquid ethyl chloride, which expands into an expansion chamber

>Its power source is an internal hermetically sealed capsule containing a mixture of gaseous and liquid ethyl chloride, which expands into an expansion chamber as the temperature rises, compressing a spiral spring; with a fall in temperature the gas condenses and the spring slackens. So it's basically a clock powered by a really simple Sterling engine?