Brother 1920CN - Color Inkjet - Fax Service Manual page 126

Selectors 6 and 7: Dial tone detection in PABX
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These selectors activate or deactivate the dial tone detection function which detects a dial tone
when a line is connected to the PABX.
Setting both of these selectors to "1" activates the dial tone detection function so that the machine
starts dialing upon detection of a dial tone when a line is connected.
Other setting combinations deactivate the dial tone detection function so that the machine starts
dialing after the specified WAIT (3.5, 5.0, or 7.0 sec.) without detection of a dial tone when a line is
connected.
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