Sughrue, Mion, Zinn, Macpeak and Seas
Tone signal detectors
 A tone signal detector for use in paging receivers, transceivers, mobile radio equipment and the like is disclosed. Received tone signals are waveform-converted to generate complementary gating pulses. These gating pulses are used to gate clock pulses to one of two counters, each of which produce a detecting pulse upon counting up to a predetermined number during a predetermined time interval. A detecting pulse from one counter resets the other, and a detecting pulse from either enables a third counter to count clock pulses. This third counter will produce a detecting pulse upon counting up to a predetermined number during a predetermined time interval. The first and second counters enable the tone signal detector to yield detecting pulses without being adversely affected by threshold variations in the waveform converting circuit, while the third counter examines frequency deviation of incoming tone signals. 
Nippon Electric Co., Ltd.
H G G H
H04W G08B G01R H04Q
inventional inventional inventional inventional
Toshihiro
Mori