FSK Demodulator Using LM565

The FSK demodulator is the electronics device that converts the FSK signal to serial digital signal. To transmit digital serial data we use FSK modulation and to get back the digital data at the receiver, we need to demodulate it. Here is the circuit:

The main component of this circuit is LM565. For mark /space coding, this demodulator circuit uses 2225/2025  Hz. This frequency is the answering frequency of BELL  113, 108, and 103 standards. [Schematic diagram source: National Semiconductor Application Notes]