switching AC power to DC power

[rotamp]

I am putting together a Security Camera System in my residential house. City Power service is very sporadic.

The whole system is now powered by AC power..but when the power is out...my facilities are not protected...

I have a complete set of Solar Power System...
....I am consuming less than 3 amps on a 9 volts system.

question.help:
What would I be needing to install between the existing AC Power sistem to "switch" over to DC power system when poer is out.

 

[OperaHouse]

Often the 9V is a relative value and not a specific voltage. The 9V batery source would be isolated by a diode. The 9V AC power would be slightly higher in voltage. The camera would normally run off the higher voltage and seamlessly switch to the battery voltage when the AC dropped out.

 

[jhudler]

Why not look at a UPS (Uninterruptible power supply).
THIS could power not only the camera, but the monitors, and records as well. A 1000VA or 2200VA would be perfect.

See

http://en.wikipedia.org/wiki/Uninterruptible_power_supply

I have two APC 3kVA UPS's with extended battery packs with run 2 seperate curcuits in the house.
Also have a 10kVA standby generator on the whole house (sans range and cooktop), and only runs when commanded or when the UPS's report low battery condition.