Recognition circuit for traffic broadcasting signals - uses pilot signal modulation filtering demodulation and comparison with modulation signal retrieved in demodulator

摘要

The recognition circuit is intended for traffic signal decoder in motor vehicles. A pilot signal is modulated by several appropriate signals. The pilot signal is separated by a filter whose output signal is amplified and applied to an amplitude demodulator. The demodulated signal is applied to an evaluation circuit compares modulation factors in order to recover the code. The pilot signal from demodulator is compared with the modulation signal retrieved in another demodulator. In order to transmit the sender or pass code, one signal path preferably a bandpass filter for the operating frequency range (20-60 Hz), and possible pass filter for the pass code frequency.