[Reaver]

Hmm, couldn't the bar/tumbler be made out of a non-conductive material that when turned in the correct direction moved something to disrupt the circuit?

Not at the length to Amp ratio. Amperages to funny things when you get up to that level of an electro magnet. The bar would have to be over 4 inches long, and made from either ceramic, wood, or other substance.... almost all metallics conduct, and conduct well.. Just a large bar would place a high amount of torque pressure on the key, which most likely bend it.

Possible is was a relay system, but then you would have a delay between the key turn and the maglock turning off.... mind you, you probably wouldn't notice the delay as to actually notice it, you would have to be pushing on the door at the exact instant you were turning the key, and timing the whole thing.... which would only be in the .75 to 1.5 second range...(an eternity for electricity)

[Blue Rose]

Conventional lock triggers relay.  Relay triggers contact in power supply.  Maglock turns off, after a momentary delay for the signal to get through.  It's inelegant, but  doable.  However, unless you're, like, in a hotel or something where the aesthetics of an old fashioned key lock are something you value, there's no reason to ever do that.

If you're looking for a simple means of disabling the lock, if you know the design, you may just be able to cut to the chase, take out a torch, and melt your way through the wiring going to or from the power supply.  Safest point would be the 120V going to the transformer, but really, there are a lot of single point failures you could, with a moment, take advantage of to disable the lock.  Not gonna be subtle, but it's not as loud as taking a step to the left and blowing down the significantly less reinforced wall.

That is, of course, assuming you know where to find the wire you want.