The Dial Barring Lock; The Optical Signaling - Alphatron AlphaConnect Classic Operation Manual

3.3.8 The dial barring lock

Note Not integrated in all types of built-in telephones.
The dial barring lock locks the keypad and thus bars unauthorized persons from making outgoing calls.
The blocking (pos. 0) resp. unblocking (pos. 1) of the keypad is only active when the operation has been made with
the receiver replaced or when the hook switch has been activated after-wards. Of course, you can continue to answer
incoming calls.

3.3.9 The optical signaling

Your built-in telephone is equipped with an optical signaling. The green LED on top right gives visual signals according to
the rhythm of the tone. That is how the tones of several telephones which are installed side by side can be distinguished.
43 | Operating of telephones