PROGRAMMABLE DIGITAL TONE DETECTOR

摘要

A plurality of up/down counters are controlled by a programmed digital reference signal. The combination of a high select signal and a high input signal causes any one of the counters to increment (up) by one count while a combination of a high select signal and a low input signal causes any one of the counters to decrement (down) one count. A threshold detector signals on output when a specific combination of the counters reaches a predetermined combination count signifying correlation of the programmed reference with the input tone over a predetermined number of cycles. The phase of the input may be determined by noting which of the counters reaches the predetermined threshold.