General Instrument DSR-4800 Operating Manual page 38

Front Panel Controls and Menu Display
Display (EXT 2) Menu 1, Edit Option 5
,
The default audio signal is a multi DTMF tone (12345) at +18
dBm. Use the blank area to turn on/off the tone.
Note this will interrupt the receiver's current audio output until
the user turns off the test signal.
Display (EXT 2) Menu 1, Edit Option 6
,
This test will alternate the external two contact closures on and
off, at 1.0 second intervals; when on forces them to close, when
off operates normally.
Display (EXT 2) Menu 1, Edit Option 7
,
This menu will be erased.
DSR-4800 Operating Manual 30