Phone Line Trouble

Hey Folks,

I’m new to the ‘fire panel’ world and I need some help. I’m an electronics tech by trade and do network cabling but phone is not very common to me.

Our church recently purchased a building with a SIMPLEX 4010 panel and we’re having trouble (pun intended?) with the phone lines. One in particular is causing me grief. They are connected to a DACT card. The RJ31x seems to be connected properly and the phone company tech said it tested fine.

Our secondary line goes into trouble whenever any phone but one is used . I’ve traced all the line as best I can, swapped phones, and isolated phones as best I can, but still can’t find the fault or why only 1 phone can be used. Can anyone tell me the voltages I should be seeing at the RJ31X (on hook, off hook, what does the panel want to see, etc)? We’re thinking a short or crossed wire somewhere but it’s an old building and the wiring is a mess with many daisy chains and hidden splices.

I talked to the previous owner and they also had this problem “sometimes” but ignored it and now I need to fix it.

I’m very close to rewiring the phone system but it will be hard to do in a finished, older building and have it look good (I’m fussy!).

Thanks for any advice you can offer!


Definitely needs to get fixed… Usually fire panel phone lines come straight from the phone provider and never should interact with the rest of the phone system in the building… Now that being said, most businesses are dropping off of the old analog POTS way of monitoring fire panels in favor of something like Cellular ( or Radio if your area supports it ( Not only are these modern technologies that are often more reliable than analog POTS, however they are usually cheaper too.

Might want to contact your fire alarm service company and have them give you a quote on monitoring. Two dedicated POTS lines are expensive, and the lack of maintenance from the phone company on copper lines often relates to most issues people have with monitoring via phone lines.

You need to make sure that your two phone lines are both 2-way DID (direct input dial) lines. Ask the phone tech to verify this. Your phone lines may both be ok and your dialer device may be defective. If you have verified the POTS lines are good at the FACP (make sure the phone guy checked them all the way to the FACP not just to a phone punch block) then your dialer card may be bad. I have had phones guys check to a block and not to the FACP and pronounce lines good only to find them dead at the FACP.

As the previous poster indicates, POTS lines are being abandoned by some phone companies but they are still available in many areas. Your alternatives are Cellular Dialer, Radio Communication or IP internet communication devices. All of these are code compliant but you must of course have two outgoing “ports” from your FACP in case of failure on one port in other words redundancy. Many people say POTS are not as reliable but I do not agree with that generally. Maybe in some areas this is the case but where analog POTS exist and are properly serviced, one usually has working POTS lines even when local power goes out. This is also usually true with Cellular towers but not always. Eventually POTS will be gone so you need to research alternatives now. I usually go IP when a building has it’s own router/server as there is no monthly fee other than the monitoring service unlike with Cellular phone numbers.

I would make sure that their phone lines havent been updated to digital or fiber optic
As i have seen all sorts of weird issues when part of the system is digital and is converted to analog