A security system for an environment from which a power supply at a first voltage level is derived, said security system comprising a first electrical circuit including a capacitor which is adapted to store charge while the security system is armed to provide a stored charge at said first voltage level, said capacitor being adapted to selectively deliver said stored charge in series with said first voltage level to provide a second voltage level for disarming the system from a second electrical circuit and switch means are provided for energising said first and second electrical circuits.
