Tuesday, June 12, 2018

Replace Cisco Power Injector with Non Cisco Power Injector

This article will show you how to use non-cisco power injector for Cisco POE enable devices, this could be Cisco phone, Cisco Access point, and other Cisco devices.

This was begun when we have several Cisco Phone 7940G without an adaptor, to get the replacement adaptor is not easy, it’s required 48V DC and 0.38 A adaptor.
Cisco Phone 7940G is POE capable device.

On the other hands, we have several unused POE injector Motorola AP-PSBIAS-2P2-AFR for Motorola Access Point AP 6521, the output is 48V and 0.35A so slightly different with Cisco Phone adaptor.

Because I see that the difference is slim I am sure that using Motorola power injector on Cisco phone 7900 series will work fine.

When I plugged the cable from Motorola power injector nothing happened with Cisco phone, so I quickly unplugged because I remember there is a 48 volts current that may destroy devices if not connected properly.

After searching on the internet I found that Cisco using different pin configuration, that is why Cisco POE devices must use Cisco power injector cannot use power injector from a different brand.

RJ-45 pin cable configuration

Knowing this I make little modification with standard PIN configuration on the RJ45 connector and it works with the following configuration:

As you can see on above picture that the cable color is:

Pin 1                Pin 2    Pin 3             Pin 4               Pin 5              Pin 6        Pin 7                  Pin 8
Orange/White Orange Green/White Blue                Blue/White    Green      Brown/White     Brown
Orange/White Orange Green/White Brown/White Brown            Green       Blue/White        Blue

This pin configuration is work and this should work with another power injector from a different manufacturer to work with Cisco devices that able to use POE.

Although UTP cable has an RJ-45 connector each has 8 cable/pin, only 4 are used for data. Pin 1,2,3, and 6.
Pin 4,5,7,8 are reserved for telephone usage.

OK, this wraps up my posting on Replace Cisco Power Injector with Non-Cisco Power Injector I hope you find it useful. Let me know in the comment section if you having trouble implementing this. Please share this article.


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