Security & Fire Protection Systems/Radionics D4112/D420 Communication Problem



I have an old Radionics D4112 Controller with a D420 Command Center.  It has worked fine for 20+ years including no problems communicating with our monitoring after switch my phone service to Comcast's VOIP 3 or so years ago.

A few weeks ago the fire alarm went off due to smoke from the kitchen stove. When I called the monitoring service to tell them all was fine we found out the system never communicated the fire alert to them.  I have tried several times to re initiate communication by unplugging the system power from AC and battery, rep lugging it in and then running a Command 41 system test.  

Unfortunately the monitoring service is saying that all they are getting is a "Low Battery Rest" message over and over but no full set of test data.  They are telling me that believe that it is an incompatibility of the older system with Comcast's VOIP and that I need to replace the controller and command center with a newer episodes model at a cost of over $1000.

Does this sound right? Is it possible that it's just a bad battery?  It is a nearly 25 year old battery.  Any other less costly possibilities?

Thanks in advance for your advice.



First of all, you're going to need a new battery (regardless of what we wind up doing with your old common control).  It is true that many older systems have problems communicating on VOIP and it's recommended that you consider upgrading.  There are a plethora of choices out there, and some don't even require a phone line (you can use a cellular option to communicate with the monitoring station).  VOIP isn't a good idea to begin with because the modem's battery typically lasts about 4 hours in a power failure.  Not sure if you want your security system to be compromised when that happens (or when they decide to take down the network for "upgrading" like a local provider does here every day around 2:00 AM in the morning.

Let's go with the battery first and see if we can't wake up the system enough to provide you with reliable communications to the monitoring station.  You can source sealed lead acid units from Home Depot and Lowes.  If you have room, go for the bigger 7AH unit (sometimes listed as 7.2AH).  Get back to me (or give me a call at 1-888-340-3473 - toll free in North America).

---------- FOLLOW-UP ----------

QUESTION: Thanks for the quick response!  I went ahead and replaced the battery as you specified.  While doing so did eliminate the keypad from beeping every hour even after pressing Command 4, it did not fix the communication problem.  It is successfully calling the monitoring service but continues to send only the "low battery restore" error repeatedly until I disconnect the phone line.  About 30 minutes after disconnecting the phone line I got the keypad beep which I silence with Command 4.  It now appears to be functioning but with no way to communicate with the monitoring service.

Let's try something else first.  Your installer may have initiated something called "swinger shutdown" which prevents the control panel from transmitting more than a set number of signals within a 24 hour period (usually from a single zone).  Let's give the panel a "rest" until midnight (when the clock resets), then try transmitting an alarm to the monitoring station in the morning.  It's certainly not unusual that troubles will transmit but not an alarm signal (particularly when swinger shutdown is enabled).  You may want to try arming then disarming your system in the morning and going from there.

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Frank Kurz


Questions relating to Burglar Alarm and Security Equipment, Fire Alarm and Extinguishment Systems, Access Control, CCTV Systems, Installation, Service, Testing, Verification


30 years installing, servicing, and testing security, access control, extinguishment, and fire alarm systems

Chair of ULC Working Groups for Fire Alarm Testing (CAN/ULC-S536) and Fire Alarm Verification (CAN/ULC-S537), Executive Director of the Fire Protection Technicians Network (

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Associate in Science; Emergency Systems (University of British Columbia); Aircraft Maintenance Technology (BCIT)

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