Amtszusatz mit automatischer Schlußzeichengabe How does it work?

[kabel]

I got the question, but have no answer. Do you know what may trig this function? When did they introduce that?

[rv12p2000]

Hello

The automatic telephone principle is based on the open or closed current loop

The power supply is based on the use of a central battery

see electromechanical automatic telephone training document

Regards

RV12P200