[asterisk-users] OT - Integration with building intercom systems

[Olivier]

Hi,

Now and then, I'm facing environments in which it could be helpful to
integrate building intercom systems with Asterisk.

Those intercom systems are made of :
- a main panel, showing company names and equiped with a speaker, a
microphone and an optional video cam
- a doorstrike
- several intercom phone with an optional monitor and with a button
triggering door's opening,
- maybe other hidden components I'm not aware of.

I've noticed that these intercom phone are connected to the main panel
through a 4 or 5-wires cable.

More precisely, for the video case I have in mind, it's a 4-wires
cable: 2 thick wires (for energy ?) and 2 thin wires (for voice, video
and command).

Is there a standardized protocol available to run  voice, video and
command on 2-wires and most probably used by  intercom systems ?

Would you say it's possible to install several intercom phones on the
same line, both ringing at the same time (but only one of them being
able to answer) ?
If positive, is it possible to connect one intercom line to asterisk
and let an asterisk user talk or watch visitor before opening the door
(through a DTMF sequence, for instance) ?

Regards