Elvox 6209?

[briped]

My intercom is an Elvox 6209, which I've been wanting to do exactly what you've done, but lacking the knowledge.

I found this manual for it.

Here's several pictures of the intercom.

[PricelessToolkit]

I am not sure and it is hard to say something without a schematic or without testing with a multimeter. 1. if just hacking together you can try and connect the input optocoupler to "A- and CA" if the red wires go to the "doorbell loudspeaker". 2. you can connect SSR wires to "Lock button directly". And i hope you understand that I cannot give any guarantee that it will work.