What is a Fax Demodulator?

Last Update: August 9th, 2021

A fax demodulator is a device that can be used to intercept fax signals, either over a phone line or a radiofax signal.

The difference between a fax demodulator from a regular fax machine is that the fax demodulator can only be used to observe the fax signal – it does not participate in the fax handshake or two-way communication that occurs between fax machines.

The term “fax demodulator” can be used for any fax demodulator, from the interception of analog signals to the digital and ip based signals that occur over a T.38 fax connection.

Use of Fax Demodulators for Legal Purposes

A fax demodulator (either a software or hardware version) is commonly used to intercept fax signals over PSTN communication lines. An example of this software is found from the company Vocal Technologies.

The use of a fax demodulator is primarily under the umbrella of laws regarding wiretapping in general as PSTN and telephone communication lines transmit fax signals.

Additional Resources:

• Fibre Optics Weekly – Fax Demodulator
• Wikipedia Article on the Fax Demodulator

More Fax Technology Descriptions:

• G4 Compression – Compression format for fax signals
• Radiofax HF Fax and Weatherfax -Fax Transmissions over Radiowaves
• T.38 -ITU recommendation for faxing over IP
• Fax Demodulator – Unit for Intercepting Fax Communication