"Security systems (including fire, intrusion, access control, and voice alarm) typically contain an AC-DC power supply to deliver power to the system and to charge and maintain 12V batteries, which provide the “secondary source” during a mains failure. The combined power supply-charger-battery system represents a key component of such systems in terms of cost and contribution to system reliability. For the SME manufacturer and installer, the manufacturing, inventory, document control, and service costs associated with the provision of a wide range of power supplies to address the market is significant. In addition, as amendments are made to the applicable EN standards (EN54-4/A2, EN50131-6, EN60849, etc) manufacturers are often required to re-design, re-test and re-certify each power supply design, which represents significant actual and opportunity costs. As such, SME consortium members have identified a need to address the costs associated with existing security system power supplies, and at the same time significantly improve the manufacturability, reliability and the feature set of these key components. The stackable (load sharing) approach offers increased reliability through design and redundancy and cooler operation by spreading component heat over a larger surface area. Manufacturing costs are minimized via the manufacture of high volumes of a common module to suit a wide product range, and the need for only one test fixture and test procedure. The approach also enables a given system to configured for a range of standby times (eg 24 to 72 hours) as required by the customer. SME participants plan integrate the SECURITAC power supply as a key component in their own products and installations, and to sell it to other manufacturers in the form of an OEM module."