PoE Switches and Subscriber modules

I have a few PoE switches http://www.cdw.com/shop/products/defaul … EDC=723802
Just for S&G I tried to power a 2400SM wth the switch, which failed miserably. That leading to these questions.

1. Does Motorola use standard PoE?
2. Has anyone found a PoE switch that will power a SM?

Typically, POE switches provide 48VDC, Canopy units require 24VDC. I have several systems running at 12VDC, but current draw is double what it would be @ 24VDC…obviously due to OHM’s Law…P=VI

I am assuming you had a typo, PoE is 48VAC not DC, I was hoping to go the opposite direction that you did on the voltage, simply for easy installations. What did you use for a 12V supply?

Ever have one of those posts where you show your ass? Yes PoE is 48VAC, but canopy is powered by DC. I think I will go back to lurking for a while!

My systems currently running at 12VDC are running on solar. All that i did was cut the wall plug off, and tie the wires directly to 12volts. It has been a while since I was out to site, but I’m pretty sure we’ve got 2 - 100watt panels and 4 100Ah batteries running an AP and SM. Haven’t had any issues yet, other than field techs not knowing ohms law and using too small of fuses!

PS. Pretty sure PoE IS DC voltage.

Thats funny, I received my training in the Marine Corps, its been 15 years since I have had any electronics education. The crazy part is that I can still spew out useless information like the formula for the resonant frequency of an RF choke.

When you are running at 12 volts, do you see any degredation of performance? Does the link show any difference between 12 and 24 volts?
I have a 5.7 BackHaul and it is the older P7 board. I have them on the Canopy wall power supplies plugged into an APC 200 UPS. Every time the UPS goes to battery, it restarts the BH. The UPS has brand new battery and I have tried a second UPS with the same results. I want to put a 12V battery under it and a trickle charger instead of the UPS to power the unit. I think that will work out for this setup.

Any ideas or similar setups welcome…


All of the 12VDC systems I have running have been installed for over a year now with no issues with the link performance whatsoever.

If you are concerned about running a BH on 12VDC, then why wouldn’t you get two batteries, series them and charge them @ 24V?

APC ups systems are known to cause issues with certain equipment when they switch from AC to DC. I have had one client that ended up changing out about 50 APC 1400VA for the same reason. Their issues were with cisco switches cycling power and/or locking up. The cause of the problems is the fact that there is a few milliseconds in the switchover, where there is actually no power output.

The solution to this is to utilize an “online” ups. I believe one of the most common brands is Powerware.

Hope this helps.