FTZ 123 D 12
The FTZ 123 D 12 is a common interface for telephone systems in Germany for connecting a door speakerphone , originally controlled by the Central Telecommunications Office (FTZ).
The "123 D 12 framework for systems according to equipment 1" from January 1988 contained the relevant specification from the Federal Ministry for Post and Telecommunications , which stipulated for the interface:
- no access to the public telephone network ,
- DC -free AB interface ,
- 2 potential-free relay contacts for at least 24 volts and 0.3 amps , of which
- 1 normally open contact with at least 3 seconds on time for door opener ,
- 1 normally open contact for other purposes,
- Operation of the door opener using the pulse dialing method .
How the signaling takes place remains open. The specification is sufficient if a separate bell system is required and the door intercom has to be called.
Individual evidence
- ↑ Helmut Kropp: Door hands-free systems and the "123 D 12" . BATELCO GmbH. November 2002. Retrieved September 14, 2012.