Error correction mode (ECM) is an optional
transmission mode built into Class 1/2/2.0
fax machine
Fax (short for facsimile), sometimes called telecopying or telefax (the latter short for telefacsimile), is the telephonic transmission of scanned printed material (both text and images), normally to a telephone number connected to a printer o ...
s or
fax modem
A fax modem enables a computer to transmit and receive documents as faxes on a telephone line. A fax modem is like a data modem but is designed to transmit and receive documents to and from a fax machine or another fax modem. Some, but not all, fa ...
s. ECM automatically detects and corrects
errors in the fax transmission process that are sometimes caused by
telephone line
A telephone line or telephone circuit (or just line or circuit industrywide) is a single-user circuit on a telephone communication system. It is designed to reproduce speech of a quality that is understandable. It is the physical wire or ot ...
noise
Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arise ...
.
The page data is divided into what is known as Octets (small
blocks of data). Once the
receiver has received all the Octets it examines them (using
check-sums) and then advises the transmitting fax of any Octets that are in error. The transmitter then need only resend the blocks in error rather than the whole page. This generally means an ECM coded fax will be more likely to succeed in transmitting a copy of the page(s) on a noisy line. ECM is the norm rather than the exception. Some fax machines have the capability to enable or disable this function.
Fax
Error detection and correction
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