The internal number of a fax is assigned in the text box Number. The Caller ID is the name or number the caller sees on the fax display. For analog faxes, the Hardware Port needs to be set. The hardware port is the physical hardware port this fax is connected to.
The advanced options for analog fax configuration allow activating polarity switch and busy detection.
In some countries, a polarity reversal is used to signal the answer or disconnect of a phone line. Performing busy detection can be useful either for detecting hangups or for detecting busy lines.
Click Save to finish the configuration.