See also:

DTMF suffix dialing
DTMF suffix dialing can be used for gaining access to network services or for controlling devices, e.g., to make a remote inquiry of an answering machine. The DTMF code is needed for this purp ...

Indicator/warning lamps
The indicator lamp flashes: DSC controls the drive forces and brake forces. The indicator lamp lights up: DSC has failed. ...

Telephone
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