How does a trap that electrocutes rats work?

I understand the rat steps on a plate and a 2nd contact completes the circuit. What voltage is used?





I found a rat got free of a spring trap and bled to death close by. It must have died in pain.





IF i wired the trap with a voltage doubler circuit using the mains I will have 680 volts. Then if the rat is not killed by the spring it will die from the shock.





I know the trap will need protection to prevent me coming in contact with the live plate. The power would kill a human let alone a rat!How does a trap that electrocutes rats work?
The one we used ran on batteries. It really wasn't all that strong.