Key operated mortise cylinder switches can restrict use of electrically operated entrance control systems, alarms, electric locking devices and other similar equipment. Actuation of switch controls can be limited to authorized key carrying personnel. Ideal for after hours access into buildings, such as apartment entrances with magnetic locks and time controlled locking systems. Key switches can also be used to authorize by-passing or shunting of door alarms and delayed release exit control systems. Other applications are security interlock override to restricted areas. The mode selection of day / night automatic door operating systems can be controlled with key switches.