A temp. monitoring switch has a cylindrical housing (2) inside which is a bimetallic disc actuator (12) that operates together with a snap action spring dish (13). A moving constant (9) engages against a fixed contact (8) to maintain a healthy circuit. When the temp. exceeds a set level the bimetallicdish inverts to break the circuit. In this position the bimetallic dish causes a thermistor (16) to be supplied to maintain a small healthy level to hold the unit in the open unit condition. A manual reset is required to restart operaiton.
