Because I didn’t want to rip the court between my house and the gate (where the door phone should be get installed) I was searching for a solution to operate a door phone without a physical telephone line to it.
My main idea was to integrate the door phone into my exisiting SIP (VOIP) environment which is reachable by WiFi (WLAN). There exist door phones with so called a/b interfaces that can be connected like any other phone to a PBX (private branch exchange, =telephone system).
Based on this I thought it should be possible to connect the door phone to an ATA (analog telephone adapter) that connects to the SIP server via WiFi connection.
Unfortunately these adapters are very expensive so I looked around for an alternative solution and finally found one: BCM96348GW based ADSL-Router (sold as Targa WR500 VOIP and the Speedport Deutsche Telekom W500V) can be used as ATAs by installing an alternative firmware. With a little patience I got one on ebay for 1€.
After installing the new firmware I put it into the arbor next to the gate (of course you need power jack at the place you’d like to install the door phone and the ATA to get the whole installation working!)
Now you can ring my door and I could answer even if I’m far away since I am connected with my mobile to the PBX via 3G. 🙂
…but as I said this was not my main attention but not to rip the court.