Is it possible to tell if a Redundant Power Supply is plugged into a 3750 stack?

Yes, normally but it depends on your IOS version (you need 11.2(7) or later) as well as your hardware.

There are no commands for the non E series, you just plug the cable in. The switch should be connected with both the AC power cable and the RPS. Under normal operation the switch will be powered by the AC mains supply, if the supply or the power adapter in the switch fails the RPS takes over (if it has power available). It is a bit hit and miss when you want to return the power back as sometimes the switch reboots other times it doesn't. The documentation even states this. The newer 3560-E & 3750-E are a bit more clever and have extra signal wires in the RPS cable so can be configured with priorities etc:

Sample output

router# show env  OR show env all


Power Supply:


Redundant Power supply is present.


Thermal status is normal.


AC status is normal.


DC status is normal.


Board Temperature:


Warning: Board overtemperature condition detected.

If you would like to get technical, to include knowing what each pin on the RPS 2300 is used for, then you can download the manual.

Thanks Again!

No Problem... anytime. Also try

show env stack[/code]