Switch Number 9 L-Delay

Body

Switch Number 9 – L Delay, or Lead Delay. A time delay switch operating on the principle that a lead wire will stretch and break within a certain time at a certain temperature, which can be accurately calculated. The breaking of the wire inside caused a spring retained striker pin to set of a percussion cap and activate the explosives connected to it. These were supplied with a tag attached stating the number of hours delay before they would set off.