Sharp FO-1450 Operation Manual page 54

USING THE CONNECTION
How fax transmissions are detected:
Your fax detects fax transmissions in two ways when an answering machine is
connected, depending on whether the document is being sent automatically or
manually:
Automatic dialling: If the document is sent using a form of automatic dialiing,
such as Rapid Key or Speed Dialling, the transmitting fax machine will send a
"calling tone" at 3-second intervals for a period of about 30 to 40 seconds after
dialling. When your fax detects this tone, it will disconnect the answering machine,
send
a "reception tone" in response, and begin receiving the transmission,
If the transmitting fax does not receive a reception tone from your fax within 30 to 40
seconds after dialling, it will usually hang up and automatically redial several
minutes later.
Since your fax may not be able to detect the transmitting fax's calling tone until after
the outgoing message ends, it is important that the answering machine answers the
call within 4 rings and the outgoing message is less than 10 seconds. Otherwise,
your fax may not be able to establish communication with the transmitting fax before
the latter hangs up.
Manual diailing: If the document is being sent by normal (manual) dialling, the
transmitting fax machine does not send a calling tone. Instead, the person faxing
normally waits until they hear a reception tone and then presses their Start key. In
the case of an answering machine connection, they will hear your outgoing
message instead of a reception tone, and then press their Start key.
However, this does not signal a fax transmission to your fax, Instead, your fax must
use a function called "Quiet Detect Time" to detect the transmission, This function
causes your fax to disconnect the answering machine and begin reception if it
detects a certain duration of silence.
Your fax is set to automatically begin fax reception if it detects a duration of silence
of 4 seconds, When the person faxing presses their Start key, the line will go quiet,
and the transmitting fax machine will wait for a reception tone from your fax, Your
fax will disconnect the answering machine 4 seconds after the key is pressed, and
send a reception tone to tell the other fax machine to begin transmission.
If your answering machine has a fast disconnect time and disconnectsthe line
before 4 seconds elapses, fax reception will not be possible, In this case, you must
shorten the Quiet Detect Time setting as described on the following page. On the
other hand, if the Quiet Detect Time setting is too short, your fax may interrupt voice
callers if they pause during their message or if there is a period of silence in your
outgoing message,
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ANSWERING MACHINE CONNECTION