Which part is not included in the data communication system model?

The data communication system model does not include data circuits and communication channels.

Data communication system model;

1, source system:

The source point equipment generates data to be transmitted; Transmitter, usually the digital bit stream generated by the source point can only be transmitted in the transmission system after being encoded by the transmitter. A typical transmitter is a modulator.

2. Target system:

Receiver: receives the signal transmitted by the transmission system and converts it into information that can be processed by the destination equipment. A typical receiver is a demodulator, which demodulates the analog signal from the transmission line, extracts the message placed at the sending end, and restores the digital bit stream generated at the sending end; The terminal device obtains the transmitted digital bit stream from the receiver and then outputs information (for example, displaying Chinese characters on the PC screen). A destination is also called a destination station, or destination.

3. Signal:

According to the parameter values representing information in the signal, it is divided into analog signal, continuous signal and digital signal, or discrete signal.