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153 Chapter 21
About Fax Machines
If you are a first-time fax machine user, fax operation might seem a little mysterious. You will soon
get used to the unusual fax tones on your phone line, and be able to send and receive faxes easily.
Fax Tones and Handshake
When someone is sending a fax, the fax machine sends fax calling tones, (CNG tones)—soft,
intermittent beeps at 4-second intervals. You’ll hear them when you dial and press Fax Start, and
they continue for about 60 seconds after dialling. During that time, the sending machine must begin
the “handshake” with the receiving machine. Each time you use automatic procedures to send a fax,
you are sending CNG tones over the phone line. You’ll soon learn to listen for these soft beeps each
time you answer a phone on your fax line, so you can know if you are receiving a fax message.
The receiving fax responds with fax receiving tones—loud, chirping sounds. A receiving fax chirps
for about 60 seconds over the phone line, and the screen displays RECEIVING. If the machine is
set to the Fax Only Mode, it will answer every call automatically with fax receiving tones. Even if
the other party hangs up, the machine continues to send the “chirps” for about 60 seconds, and the
screen continues to display RECEIVING. To cancel the receiving mode, press Stop/Exit.
When the machine is in Fax/Tel (F/T) Mode, it answers with a short beep. After this beep, the fax
machine listens for CNG tones, and then responds with receiving tones.
The fax “handshake” is the time in which the sending machine’s CNG tones and the receiving
machines “chirps” overlap. This must be for at least 2 to 4 seconds, so the fax machines can
understand how each is sending and receiving the fax. The handshake cannot begin until the call is
answered, and the CNG tones only last for about 60 seconds after the number is dialled. Therefore,
it’s important for the receiving machine to answer the call in as few rings as possible.
ECM (Error Correction Mode)
The Error Correction Mode (ECM) is a way for the fax machine to check the integrity of a fax
transmission while it is in progress. ECM transmissions are possible only between machines that
both have the ECM feature. If they do, you may send and receive fax messages that are continuously
checked for their integrity.
Sufficient memory must be available in the machine for this feature to work.
When you have an external telephone answering device (TAD) on your fax line,
your TAD will determine the number of rings before the call is answered. Pay
special attention to the directions in the Installation chapter for connecting a TAD
(or answering machine) to the machine.