Fax Tones and Handshake, ECM Error Correction Mode

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Fax Tones and Handshake
When someone is sending a fax, the 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; they continue for about 60 seconds after dialing. 
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 LCD 
shows 
RECEIVING
. If your machine is set to the FAX mode, it will answer 
every call automatically with fax receiving tones. Even if the other party hangs 
up, your 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 your machine answers in FAX/TEL mode, the 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 machine’s “chirps” overlap. This must be for at least 2 to 4 
seconds, so the 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 dialed. 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 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 your 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 Assembly and Connections chapter 
for connecting a TAD to your machine.