Line Lock Selection
I've got the SJM ABS/TCS delete kit with line lock, but I had my own solenoid to use. I'm running a Hurst line lock solenoid and haven't had any issues yet. I don't use it very often though.
Momentary switch is exactly what it says
When you press the button, it activates the circuit, and as soon as you let off, the circuit is deactivated. To be track-legal, you must use a momentary switch for safety. If you use a standard on/off switch, if the button is accidentally left in the on position, it won't return to the off position to deactivate the line lock and well... that could be dangerous. 


