Analogue tone signal detection system

摘要

The detection system detects analogue tone signals of given frequency by converting the analogue tone signals (ts) into digital period duration-oriented tone signals (dts) and counting the period duration. The count representing the period duration is evaluated using an evaluation time frame beginning at a count value corresponding to the lower frequency limit of the analogue tone signals and ending at a count corresponding to the upper frequency limit, with the analogue signals of given frequency indicated when the count coincides with the evaluation time frame.