A µProcessor controlled, sub-audio frequency signalling processor to provide an outband audio and digital signalling facility for PMR radio systems.
This device caters for the transmission and non-predictive reception of:
●Continuous Tone Controlled Squelch (CTCSS) tones and other non-standard sub-audio frequencies.
●Non-Return-to-Zero (NRZ) data to facilitate Continuous Digitally Coded Squelch (CDCS/DPL) system operations.

To achieve these functions, the FX805 has on-chip:
●A non-predictive CTCSS Tone Decoder and CDCS sub audio signal demodulator.
●A CTCSS/NRZ Encoder with Tx level adjustment and lowpass filter output stage with optional NRZ pre-emphasis.
●A selectable sub-audio bandstop filter.
●A Notone (CTCSS Rx) period timer.