The thermostats are electromechanical controller for monitoring the temperature. The devices are in a liquid-filled measuring system, which consist of the temperature probe, capillary, Bourdon tube or capsule, and a switch. The temperature-dependent change in volume in the measurement system is converted by the spring or of the capsule in a rotary or pushing movement without transmission gearing. The rotation of the pointer shaft or the stroke of the capsule, activates a switch which opens or closes  the contacts.