Coin lockout coils are a holdover from the electromechanical pinball days. On one of those pinballs the coils served 4 purposes:
1. To reject a players coins if inserted when the machine was turned off. In the old days there were no "On-off" power switches installed on the machines--you had to unplug the machine to turn it off. When plugged back in nothing would light up. You had to put coins in it to turn on the lights again.. a sort of Catch 22 situation.
2. To prevent getting free or extra credits if a coin was inserted while the score motor was in the middle of a cycle.
3. To prevent getting free credits if you kicked/banged the hell out of the coin door in an attempt to get free credits from vibrating the coin switches. If you banged the coin door hard enough, an "anti-slam" weighted switch would open thus killing power to the lockout coil and the coin relay.
4. In the event the "coils" fuse blew the lockout coil would block coins thus the location owner would call for repairs.
I strongly feel that lockout coils should be brought back. With expensive machines like "Let's Go Jungle" that cost alot to play and have a very long power up sequence due to the fact it uses a computer. If a person puts in coins while it's still powering up they lose their money.