TM500 high-power compartments
The TM504, TM506 and TM5006 each have one compartment that can take high-power plugins.
A metal cover to the left of the backplane connector pushes a switch in the rear of a high-power plugin in that compartment.
In the other, low-power compartments, a hole in the cover prevents this. Smaller mainframes like the TM503 may have no such covers at all.
In the high-power slot, the 25 V transformer windings can supply at least 1 A each instead of 0.5 A, and the +11.5 VDC/17 VAC supply is rated for at least 3.6 A instead of 1 A. See the TM500 Series plug-in interface for more details.