The thermo switch O is used whenever switch-on function is needed, caused by overheating or increasing temperature. Specific applications include: cooling fan, alarm signal, controller, timer.

The thermo switch O operates not current sensitive. Temperature detection is realized by a bimetal snapdisk. When the switch-on temperature TE is reached, the bimetal disk will snap over to close a contact system. After cooling down and reaching the cut-off temperature TA, the bimetal disk will automatically return to its initial position and open the contacts again.