Abstract: A safety circuit which connects a condition responsive circuit to a cyclic signal detecting circuit. In order to provide the cyclic signal detecting circuit with a continuous cyclic input, the condition responsive circuit and a cyclic redundancy checker is provided. The cyclic redundancy checker identifies a specific series of logic bits from the condition responsive circuit and responds favorably only to that series of logic bits. If any other series of logic bits occurs, the cyclic redundancy checker of the system ceases to function, thereby causing the cyclic signal detecting circuit to cease to function and it in turn opens a series contact to deenergize a critical load in a control system.

Abstract: A microprocessor control system for monitoring and controlling a plurality of different parameters or features of a large number of like-kind entities, each characterized by such parameters or features. The control system is particularly suitable for automatically controlling on an indiviudal room basis, parameters within hotels/motels such as: counting the number of outgoing calls, paging guests having messages and controlling room message waiting indicators, placing wake-up calls to guest rooms at predesired wake-up times, and tracking in real-time the housekeeping and occupancy status of each hotel/motel room. Incidentally to the room status feature, telephone sets within unoccupied rooms or within rooms being cleaned are automatically disabled from registering outgoing calls, but may be used for registering emergency calls. All control functions are performed by a microprocessor under hardwire program or firmware command.