ComTekk Multi-Decoder utilizes the latest in Digital Signal Processing (DSP) technology to instantly and accurately measure the frequencies of a received two-tone paging signal or "fire dispatch tone out" signal, CTCSS "PL" tones, and DTMF codes.
Receiver audio output is fed into the computer's sound card (via cable or microphone) where an A/D converter reads the signal's instantaneous voltage 11,025 times per second. This is the sampling rate. With time and magnitude data, the software first processes each batch of samples by applying a band-pass filter or window, thereby ignoring any frequencies outside the range of 250-5,000 Hz. Another filter searches for continuous tones, ingoring noise, voice and digital communications. Frequencies below 250 Hz are generally reserved for CTCSS sub-audible tones used to access repeaters and limit interference. DTMF tones, most commonly known as "Touch-Tone" (tm AT&T) are used for paging, ANI and remote control over radio, and for dialing on telephone lines.
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