adaptor and battery, switch from one to the other

[simon1138]

hello,
if a pedal has an adaptor and a battery option. how does it switch from one to the other? when you plug in adaptor is there a switch that removes the battery from the circuit. i have a flip flop in my broken pedal and it is used to activate the pedal, i am not sure if it is also used to change from adaptor to battery.
i havent been able to find a description of this anywhere, any help would be great thanks
simon

[antonis]

Both 2 red wire DC jack lugs are shorted without DC plug in..
(so circuit is fed from battery..)

When DC plugged in, battery's wire is disconnected (via internal DC jack switch) so circuiit is fed via external PS..