I have a fibre-only installation, with a 2degrees Fritzbox 7490. I have no problems with making and receiving calls from my telephone handsets via the Fritzbox's analogue phone line input.
Recently an alarm technician connected the house alarm to this analogue line (as if it were just another handset) for the purposes of monitoring. Although it "hears" a dial tone and attempts to make calls out to the security company approximately twice a minute, the calls are terminated before they even "leave" the house. The alarm dials out but is cut off within less than a second - either by itself or by the FritzBox, I can't tell. The FritzBox logs an outgoing call attempt each time, but shows the duration to be only a few milliseconds.
Strangely the alarm tries to dial out when there's a call currently underway - I would have thought it would test the line for a dial tone first before trying to dial? Could this indicate that the alarm isn't able to "listen" on the line - maybe it is not wired correctly? I believe it's just using the two wire telephony standard though, so that would be difficult to mess up.
The alarm company seem to be entirely unfamiliar with this situation and would prefer to install an IP module. I'd like to find out if I can get the analogue phone line method working though, as that module is almost $300, and it seems like it should work as there's definitely a dial-out attempt being made.
Has anyone had any experience with this and can give me some pointers please?