First I am a telephone guy, I dont do security or alarms.
I have a customer that we just put in a new Toshiba and T1 with 6 digital lines out of an Adtran unit. Four lines go on the system, one for fax, and the other for alarm system. The alarm pad at the front flashes & chrips every 20 seconds, it did this before on the local copper lines too. The vendor stated the line shows a voltage drop is causing it and claim this issue is not a problem with the equipment.
Like I said Im a telephone guy but this seems like a equipment problem, they have no problems on the voice lines or faxing and nothing else is using the security line and we have switched lines that it uses and the problem still exists.

Anyone have any thoughts or suggestions?