Circuitry for characterizing speech for tamper protected recording.

摘要

Circuitry usable in a tamper protected recording system for characterizing audio signals at the time of recording including a filter (10) for selecting a portion of the audio signal, a zero crossing detector (14) to detect zero crossings, a threshold detector (16) to determine when the threshold of the detector is satisfied, a first microprocessor (18) for counting the zero crossing detections for successive time intervals and determining for each of the time intervals whether the threshold was satisfied and a second microprocessor (20) for converting the counts and threshold information into data signals that can be recorded with the audio signal.