Wired Security systems (eg DSC, Elk) are powered by an external power supply, and then in turn they supply power to 12VDC peripherals such as keypads, zone expanders, motion sensors, glass breaks, smoke detectors. This auxiliary power from the panel is usually limited to around 1A (check the manual for details). In most cases this is sufficient but when in doubt, add up the current draw from each keypad and powered device to see what they total. This information can be found in the device specs or in the manual for each device. If they all add up to more than the panel provides you will need an additional power supply.

As a wired alarm system needs a battery back up the power supply really consists of a plug-in power adapter (eg. part# TP4016) and then a charging circuit like DSC PC1520 and then a battery. Recommended 4-8AH size, such as ELK-1280 for example. Also an enclosure is recommended.  As another example, ELK-P112NT would include everything except the battery.

This works fine however doesn’t provide ‘supervision’, meaning if this secondary power supply fails, the main alarm system won’t know about it. For a better solution, go with a supervised power supply, such as PC5204 which can report to the panel in case of a failure.

 This is the example for DSC. Other companies such as Elk also offer regular and supervised power supply options.