Brief Description
The FX375 is a Low-Power CMOS LSI microcircuit designed for Tone Operated Voice Privacy in communication systems.
This half-duplex device consists of a Fixed Frequency Voice Band Inverter interfaced with a Continuous Tone Controlled Squelch System (CTCSS) Encoder/Decoder, whose allocated tone is used for voice privacy and audio squelch operation.
Frequency Inversion is achieved by modulating the input audio with a fixed carrier frequency to exchange the high and low frequencies of the voice band, making the resulting audio output unintelligible to receivers not equipped with a compatible system.

FEATUREs
• Tone Operated Private/Clear Switching
• CTCSS Tone Encode/Decode
• Separate Rx/Tx Speech Paths
• Fixed Frequency Speech Inversion
• µP Compatible Interface with Serial or Parallel Control Loading
• On-Chip Pre- and De-Emphasis Filtering in the Tx Path
• 38 Programmable Tones + 'NoTone' Facility
• Audio Path Filtering (300Hz – 3033Hz)
• Low Power 5V CMOS