Security & Fire Protection Systems/Radionics D4112 alarm


I know this system is ancient, but it's been (and still is)very reliable. After a recent one-hour power outage, the system has been working normally, except after being active all night, in the morning the control panel beeps (a steady beep-beep-beep). When the front door is opened, the control panel starts a steady alarm beep sound, and the system will disarm normally with the code. The steady beep will stop after entering [command][4][enter]. I suspect the battery (it is old) but it tests at about 13.2v. The power supply for the battery charging system tests OK, too, and the green AC light is on. If this system is too far gone to rescue, will most of the newer basic systems support using the outside siren from the Radionics unit?
Thank you.

Hello Barry, and thanks for your questions.

To answer your last question first, yes, your existing outside siren will work with a newer system, if one is needed.

But before considering system replacement, let's take a look at your battery. I suspect the battery too, and it's worth your while to try that before investing in a new control panel.

Batteries must be tested under load, without AC power applied. If this isn't done, the voltage reading is spoiled by the charging circuit.

So do a quick check. Just disconnect the AC power (unplug the transformer or take a wire off one the AC input terminals). Then take a voltage reading from the battery. You'll probably see a significant drop in the voltage. Then cause the siren to sound. This puts a heavy load on the battery. Take another reading. If the voltage drops even more, or the siren sounds weak, then you need a new battery.

A battery in good condition will be able to power the system for a minimum of four hours, and after that, be able to sound the bell or siren for a minimum of five minutes. That's the gold standard.

Your system takes a 12 volt, 6 ampere hour sealed lead-acid battery. If you need one, it's not the item you'll generally find at a retail store. Just Google "alarm battery" and you'll find several vendors online. Brand is not very important, but the specs are. And shop around, paying attention to the shipping charges as well as price.

If you decide to replace the control panel, let me know. I'll be glad to help you choose a suitable replacement.

Best Regards,


Security & Fire Protection Systems

All Answers

Answers by Expert:

Ask Experts


Dave Neuweiler


The design and application of burglary and fire systems for homes and businesses. Helping alarm owners understand how their system works. Helping to troubleshoot false alarm problems. Questions about monitoring issues.


Over a quarter century in the industry. Experience in installation, service, and monitoring centers. Training manager for a national protective services company; director of education and training for a national trade organization for for alarm dealers.


©2017 All rights reserved.