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 system and method for generating and presenting a lesson plan comprising audiovisual materials to a classroom. The system enables the automatic connection of audiovisual output signals from one or more audiovisual resources to classroom monitors in accordance with a predetermined sequence called a "lesson plan." The lesson plan includes labels for identifying selected ones of the audiovisual resources, and control commands for controlling the selected audiovisual resources. At a scheduled date and time, the lesson plan is loaded into the system and processed to automatically connect the output signals from selected audiovisual resources to specified monitors, and also to control the playback of the resources.The system also includes a software program for generating the lesson plan and saving it for a future presentation. To assist with the generation and presentation, a database of available materials and a scheduling program are also provided.

Abstract: A system and method for generating and presenting a lesson plan comprising audiovisual materials to a classroom. The system enables the automatic connection of audiovisual output signals from one or more audiovisual resources to classroom monitors in accordance with a predetermined sequence called a "lesson plan." The lesson plan includes labels for identifying selected ones of the audiovisual resources, and control commands for controlling the selected audiovisual resources. At a scheduled date and time, the lesson plan is loaded into the system and processed to automatically connect the output signals from selected audiovisual resources to specified monitors, and also to control the playback of the resources.The system also includes a software program for generating the lesson plan and saving it for a future presentation. To assist with the generation and presentation, a database of available materials and a scheduling program are also provided.

Abstract: A system for monitoring the integrity of speakers and their associated wires using the pair of audio wires without disconnecting the speaker from the audio source. A direct current is injected onto the audio signal path and directed via a high impedance path through the speaker coil while any audio signals present drive the speaker through a low impedance path. The magnitude of the direct current is then evaluated at a central switching location and based on the value of the current, the status of the signal path is known to be either a good path, an open path, a shorted path or a grounded path. Alarm initiating devices may be connected to the wire pair and can be connected in such a way that the current on the wire pair indicates the status of the alarm indicating devices distinct from the currents corresponding to signal path integrity.