EMU-1 is an electrical booby trap switch designed to initiate mines and demolition charges by pressure or pressure release, though it can also be actuated by pull.
The underside of the flat alloy cylindrical base section unscrews, giving access to a compartment which houses a 4.5 V battery.
Two leads, for connection to an electric detonator, emerge from the side of the base section.
A central spigot assembly protrudes from the top and to one side of this is a lamp holder sealed with a translucent cover.
The spring-loaded spigot assembly has a central pressure plunger with a threaded cap on the top to give height adjustment.
The base section, spigot and plunger are earthed to the negative terminal of the battery to form one contact.
The positive terminal is connected to the bulb and a contact positioned in a groove around the lower section of the central plunger.
The spigot and plunger are held in position by a spring-steel safety clip until the device has been set.
EMU-1 is painted olive green.The fuze is normally set beneath a railway line, and the top cap adjusted to touch the underside of the rail.
As a safety feature, the lamp will illuminate if the internal contact is made; this also allows the sensitivity to be selected by adjusting the cap until the light comes on and then backing off the screw until contact is broken.
Once set, the detonator is connected to the wires and inserted into the main charge.