a device for indicating the presence of explosive or (now usually) poisonous gas.

An electrical device for detecting the presence of water.

an electrical instrument (invented by Capt. McEvoy) placed at the sea bottom to detect the presence of steam vessels in the neighbourhood.

any device for detecting leaks of fluid.

an instrument for detecting the presence of explosive mines.

a sensor consisting of one or more photocells which uses variations in the amount of light reaching the cells to detect the passage of an airborne…

(a) a heat-seeking missile; (b) a device which detects infra-red radiation and the direction from which it comes and supplies the information to…