Manual override There is a three-position switch built in to the face of the dial. For automatic timed control, governed by the tappet settings, the switch should be left in the middle position (as illustrated). The output can be switched ON at any time, by moving the switch lever to the top position, marked with a I on the dial. Alternatively, the output can be switched OFF at any time, by moving the switch lever to the lower position, marked with a 0 on the dial. The manual override is a fixed selection – the output will remain ON or OFF (as selected), until the switch lever is moved back to the middle timed position, marked with a on the dial