Integrated speaker supervision and alarm system

A supervision circuit for monitoring path integrity in an audio system, where the audio system includes a central switching location driving at least one speaker with audio signals through a wire pair connecting the central switching location to the speaker, the speaker being of the type which includes a DC blocking capacitor, the supervision circuit comprising the combination of:

• a DC source at the central switching location connected to the wire pair for injecting a current onto the wire pair without disconnecting the wire pair and speaker from the audio system;
• a DC shunt connected across the capacitor at the speaker for passing the injected DC current through the wire pair and the speaker;
• a detector connected to the wire pair at the central switching location and having an input adapted to monitor the DC current level on the wire pair to verify the path integrity;
• and
• a controller for indicating the nature of any fault detected.

A supervision circuit for monitoring the path integrity in an audio system and the status of an alarm initiating device, in which the audio system is of the type having a central switching location driving at least one speaker via a wire pair connecting the central switching location to the speaker, the speaker having a blocking capacitor associated therewith, the supervision circuit comprising, in combination:

• a source at the central switching location for injecting a DC current onto the same wire pair which drives the speaker;
• a bypass shunt associated with the speaker for bypassing the blocking capacitor and completing a path for the injected DC current from the wire pair through the speaker, so that the injected DC current at the central switching location transverses the wire pair and the speaker;
• an alarm initiating device for influencing the DC current level injected on the wire pair when activated to a DC current level distinct from the DC current level injected on the wire pair when not activated;
• a detector at the central switching location for responding to the DC current level on the wire pair and evaluating the path integrity and the status of the alarm initiating device based on the magnitude of the detected current;
• and
• a controller responsive to the status of the integrity of the connected wire pair and the speaker and the status of the alarm initiating device for indicating the nature of the current detected.