The EW is a 12-hour test clock used in the EMF, LMF, and SMA mines. This clock con-sists of the standard spring-driven German clockwork mechanism driving a rotary contac-tor shaft. The unit is designed to close electrical contacts.

The setting is entered manually by positioning an indicator disk fitted to the top sur-face of the clockwork assembly. The disk is graduated in azimuth from one to eleven in increaments of 0.5 and moves against a fixed index.

The contacts of the six contact terminal board are wired in series with the contacts located on the rotary contactor shaft.