Continuous digital code squelch system signal transmission device

摘要

The transmitter incorporates CDCSS and FSK signal generators with high and low internal impedances respectively and frequencies below and above 300 Hz. The outputs are added and passed to the radio frequency output stage via a phase-locked loop having a resistor (R1) and capacitor (C2) connected to the phase detector. At the receiver an FSK decoder is connected with a high-pass filter, a low-pass filter, an amplifier, an analogue comparator and a CDCSS decoder.