If one produces a DC circuit where should he put a diode to protect inverse voltages(e.g wrong battery conenctions)?
In any one of the battery supply lines. However if there is likely to be several instances of incorrect connection you can connect the device supply wires to the + and - side of a bridge rectifier and the AC connections now become your battery connections. It is then imaterial how you connect the battery since the bridge will "re-arrange" the polarity to the correct configuration. (You will however "lose" around 1.4 volts through the bridge)
Why is this a pole again?
Nice one Nick
Old Jock dog learns new trick from Ozzie
I think the word "poll" is being confused with "question". As in, "post new question".
I have repeatedly suggested that the "post new poll" option be removed, with no result.
jackrae:
Nice one Nick
Old Jock dog learns new trick from Ozzie
Wee Jock?
To give credit where it's due - Afrotechmods came up with that idea. 
Maybe we should have a poll to see how many are in favour of depoling