Abstract: Audio and video systems for checking safety sounds and telltales are provided. The audio system includes a digital signal processor with a plurality of safety sounds and a plurality of signatures corresponding thereto. A head unit controller includes a signature and volume checker to identify an expected signature of the one of the safety sounds. The digital signal processor outputs a mixed audio stream and includes a lower bit inserter to replace lower bits of the mixed audio stream with replacement lower bits based on the signature and output a modified audio stream. A lower bit extractor separates and outputs the replacement lower bits and a remainder of the modified audio stream. An audio amplifier unit receives and outputs the remainder of the modified audio stream. The head unit controller rebuilds the signature, determines whether the signature matches the expected signature, and sends an acknowledgment accordingly.

Abstract: An apparatus for measuring current carried by a conductor has a differential voltage amplifier having inputs for connection to the conductor at two spaced-apart points thereof, constituting the ends of a segment. A circuit which converts an output voltage of the amplifier into a current value incorporates a microcontroller associated with a programmable memory storing a calibration table in digital form.

Abstract: An apparatus for measuring current carried by a conductor has a differential voltage amplifier having inputs for connection to the conductor at two spaced-apart points thereof, constituting the ends of a segment. A circuit which converts an output voltage of the amplifier into a current value incorporates a microcontroller associated with a programmable memory storing a calibration table in digital form.