STM Safety Switches Switches are used to protect personnel by monitoring and interrupting the safety circuit depending on the position of the machine guard. The locking solenoid holds the guard closed until a stored energy hazard has dissipated. It can also prevent damage to a part in process due to an inadvertent machine shutdown. To meet current worldwide standards, safety interlock components cannot be easily bypassed. These switches have positive opening contacts and redundancy to guarantee that they fail to a safe state. Due to its small design, the STM safety switch with plastic housing is particularly suitable for applications in which robustness is required in combination with small dimensions.