I found this post about the original DELL setup. It is called a Redundant Power Supply:
“Installing a Dell EPS-470 Power Supply
Posted by Jeff Csisar on July 29, 2014
Installing a Dell EPS-470 extended power supply into your Dell PowerConnect switch is a breeze. The EPS-470 installs through a simple power cord and connecting power cable. The power cable runs from the back of the EPS-470 into the power port in your Dell PowerConnect 3448P or 3548P.
Below are photos of the power ports on the EPS-470 and Dell PowerConnect 3548P. They show where the connecting cables install.
In addition to being able to install EPS-470 power supplies through this port on PoE switches, the Dell 3524 and 3524 (non-PoE) can have a Dell RPS-600 power supply installed. If installed properly, the LEDs on the power supply will illuminate to alert users to the fact the power supply is sharing power. The EPS-470 works by load balancing with the Dell switch’s power supply.
Pasted from <http://refurbphoneexchange.com/blogs/phone-and-tech-blog/14977029-installing-a-dell-eps-470-power-supply\> ”
Installing a Dell EPS-470 Power Supply
_
Added info:
PC3448P EPS-470 pinout
Posted by marekm
on 5 Jul 2013 20:08
It’s just 3 pins, and I have successfully identified the +/- ones, what is the third one for? I’d like to power the switch from –48V DC telecom battery backup instead of the original EPS-470, and it works but I can’t get redundant power (both AC and DC at the same time) to work properly, I can hear a relay inside click very often (which may not be good for the hardware, so I don’t leave it running in this condition for a long time). Has anyone reverse-engineered it already?
Middle pin is positive, the pin closer to the AC input is negative, and the third pin is not earth ground for sure. Left open, it’s about 2.5V above the –48V DC rail. So it may be some kind of logic input or output (or even an analog signal for some kind of load sharing?) between the switch internal PSU and the EPS-470.
I know what I ask is not officially supported, I’m prepared to void the (already expired) warranty, I’m an electronics engineer, aware of electrical safety issues etc.
Pasted from <http://en.community.dell.com/support-forums/network-switches/f/866/t/19515176\>
http://en.community.dell.com/support-forums/network-switches/f/866/t/19515176
I’m doing some network design (which includes racks and PDUs. In several cases, I need an EPS-470 power supply to provide PoE to all 48 ports on a PowerConnect switch.
I need to know, do I need one outlet for the switch and one for the EPS-470, or after the switch is hooked into the EPS-470 do I just need power hooked into that? I just need to know whether I need one or two outlets so I plan accordingly for the PDUs.
The EPS-470 adds additional power, so you need two, one for the switch and one for the EPS.
Pasted from <http://en.community.dell.com/support-forums/network-switches/f/866/t/19589890\>