Yep they have an input-jack which has some plastic thingy that keeps the plug in place.. you can only remove the plug if you press a small red, plastic pin.
When they work properly, I was at Dave Phillips Music And Sound when I tried a BTB, the chord wouldn't come out. The lock wasn't working properly, I called the guy over to get it out, and it took him 20 minutes to get it out... I'd make sure yours is working properly when/if you get one (a btb).
Press red button in all the way, and pull the chord out with the red button still pushed in. You probably weren't doing it right. Have to hold the button down.
I know. However, it wasn't working properly. One of the salesmen had to use excessive force to get the cord out, I'm just pointing it out so he makes sure his cord locking thinger is working properly...
Yeah, he definitely needs to make sure that he knows how to use the Neutrik locking jack before he buys the bass.