Abstract: A signaling system may include two subsystems that share a common wiring backbone and provide public awareness functions. The two subsystems may be a public address system and a master/slave clock system. Remote rooms at the tail end of the wiring backbone include a speaker and a slave clock. The speakers are in communication with a control device through the wiring backbone. The slave clocks are in communication with another control device at the head end of the wiring backbone. The master/slave clock system superimposes its DC power signal and a time correction signal on the wiring backbone. Each slave clock interfaces the wiring infrastructure through a center tap of a speaker transformer which allows the slave clock to be powered and corrected via the speaker wiring infrastructure.

Abstract: A user-programmable clock is provided for executing events defined by functions executed at a particular time and selected zones and for selected schedules. The clock includes an event memory for receiving zone and schedule data from a keyboard by way of a processor wherein the event memory is segregated into first, second and third tiers of event data. The processor of th clock is responsive to the keyboard for routing zone and schedule data entered from the keyboard to one of the three tiers of the event memory. The first tier of the event memory includes a plurality of locations wherein each location corresponds to an increment of time. Means are provided for selecting data stored in the first tier of the event memory at address locations corresponding to time data received from a timing mechanism. Means are also provided for selecting the appropriate data stored in the second and third tiers.

Abstract: A master/slave clock system including a slave clock configured for inexpensive and reliable control from the master. Each slave clock has an unregulated d-c supply adapted to be supplied with a-c power from the master clock. Threshold switching means in each slave clock is coupled across the d-c supply to sense an abnormally low d-c voltage level intentionally created by lowering the a-c supply level from the master. The threshold switching means switches the clock from the normal operating mode to the set mode where time is incremented at a predetermined rate for a duration controlled by the master clock in order to controllably set all slave clocks in the system to the correct time of day. The system conveniently allows all slaves to be reset to the same time when time is reset at the master, provides for automatic recovery after power failures, and provides a convenient means for automatically resynchronizing all slave clocks twice a day.

Abstract: A user programmable clock which is both simple to program and capable of executing relatively complex events. The front panel has a display divided into a plurality of functional blocks, with an operator positionable pointer adapted to activate any block. A single keypad is used to enter data in the respective blocks designated by the pointer. The system allows programming of comparatively complex events, capable of relating a single time to any combination of days and any combination of zones. Event programming is further simplified by providing an immediate indication of an erroneous entry along with a signal distinguishing between various potential types of errors.

Abstract: An administrative telephone system for use in schools, hospitals and the like which includes a dialable administrative telephone set and a plurality of dialless remote or "staff" telephone stations having identifying numbers, interconnected by a central exchange. The administrator can dial any staff telephone station by pressing two digit buttons on the dial pad. Associated with the administrative telephone set is a digital display device having a column of display positions. Each staff telephone station has a call-in switch. The central exchange includes storage provision coupled to the digital display for registering and displaying, in order, the numbers of the staff telephone sets which have called in and thus have indicated a desire to communicate with the administrator.