FX365C

The FX365C is a 3-volt, half-duplex predictive Continuous Tone Controlled Squelch System (CTCSS) encoder/decoder microcircuit. The FX365C has integral voice-band filtering for prefiltering of Tx audio and the rejection of the CTCSS tone in receive. Under µProcessor control, the FX365C will encode and decode any one of 39 sub-audio frequencies(+NOTONE) in the range 67.0Hz to 250.3Hz. Tone frequencies and all functional commands can be loaded to the device in either pin-selectable 8-bit parallel or serial format.

A separate, Rx/Tx voice-audio path FX365C is available with a highpass (sub-audio reject) filter automatically placed in the relevant Rx or Tx voice line.

The Rx sub-audio (CTCSS) path FX365C contains a (selected tone frequency) bandpass filter and period detector providing a logic level output (Rx Tone Detect) to indicate a successful decode operation.

Rx "Press to Listen" (PTL) and Tx "Squelch-TailElimination" functions of FX365C are available in both command loading modes. The squelch-tail elimination function will provide (Tx tone) phase-reversal to minimise the annoying audio outputs that occur at the receiver on completion of a transmission.

Tone frequencies and filter accuracies of FX365C are maintained by an on-chip 1.0MHz clock oscillator employing an external crystal or clock pulse input. The FX365C, which exhibits high audio and subaudio performance with low falsing, is available in 24- pin DIL and small outline SMD packages.