a circuit that closes when power is cutoff

[flippityflop1]

i need a circuit design that closes a secondary circuit, when power is cut from a primary circuit (@ typically 6V). i don't need extremely fast switching. this isn't also going to be a backup power supply (so the secondary circuit WILL NOT be providing a continuous power to the primary). so needless to say, what i need is very simple.

 

[Hero999]

A normally closed relay.
https://www.google.co.uk/search?q=normally+closed+relay&ie=utf-8&oe=utf-8&gws_rd=cr&ei=uHWlVKf_E4jjaoSwgaAN