Description
The FX/MX465 is a 2.7 volt, half-duplex predictive Continuous Tone Controlled Squelch System (CTCSS) encoder/decoder microcircuit.
The FX/MX465 has integral voice-band filtering for pre-filtering of Tx audio and the rejection of the CTCSS tone in receive.
Under µProcessor control, the FX/MX465 will encode and encode any one of 47 sub-audio frequencies (+ NOTONE) in the range 67.0Hz to 254.1Hz. 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 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 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-Tail Elimination" functions are available in both command loading modes. The squelch-tail elimination function will (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 are maintained by an on-chip 4.0MHz clock oscillator employing an external crystal or clock pulse input.
The FX/MX465, which exhibits high audio and sub-audio performance with low falsing, is available in a D5 24-pin shrunk small outline SMD package.