CTCSS Decode should be on all analog audio modules. The code was written already and only implemented on NFM - so it should be ...

freqs_ctcss_1 = [67.0, 71.9, 74.4, 77.0, 79.7, 82.5, 85.4, 88.5, 91.5, 94.8] freqs_ctcss_2 = [97.4, 100.0, 103.5, 107.2, 110.9 ...

To allow multiple users to share one carrier frequency, many handheld transceivers employ Continuous Tone Coded Squelch System ...

The AK2345 is an IC which supports CTCSS (Continuous Tone Controlled Squelch System), compatible with TIA/EIA-603 standard.