To the various questions:
I bought my alarm system on ebay and it is a no-brand Chinese made system (Model Z64). There is not much documentation for it. Nevertheless, the fact is that the "receive call" feature of the alarm system works with the regular land line but not with the OBi device. (Calling out works without a problem)
I have a phone connected to the output of the alarm system so I can also hear the phone ring.
I tried the idle polarity reversed but it did not make a difference.
I wonder if the voltage needs to be higher than the 82 volts that the system allows (It can be set from 55 to 82). I read that the standard for a regular land line is 90VAC.
Has anyone have issues with answering machines or fax machines not receiving calls?
Any suggestions?