POE - Aironet 350 / 7940 IP Phone?

Question

Hi All, I recently purchased a POE Injector from Solwise to power my Cisco Aironet 350. Rather disappointingly, it doesn't appear to work. According to the Cisco website, the Cisco Aironet 350 should support the current IEEE 802.3af and pre-standard POE, which I would understand as meaning that it should support power injectors which do not have any 'sensing' mechanisms, such as the device I purchased:  I've also tested the POE Injector with a Cisco 7940 IP phone and have found that it will not power the phone either. Has anyone had any similar experiences or a solution to this problem? I thought the POE Injector would be cheap and cheerful way of providing power to my POE devices without having to stretch to a POE switch. Any help appreciated, RG

Mr Corbett · Accepted Answer

Not sure if it help but I have recently used a AIR-PWRINJ POE injector on a  350 with no problems, is the injector dead?

Router God · Answer

Problem solved!

Using a DVM (Digital Volt Meter) I measured the voltages on my Solwise POE injector and a Cisco AIR-PWRINJ POE injector, which I borrowed from a friend.

What I found was Standard POE injectors (Solwise) use PINS 4&5 as the Positive (V+) line and PINS 7&8 as the (V-) line. Cisco for some reason use the connection the opposite way round, PINS 4&5 as the Negative (V-) line and PINS 4&5 as the Positive (V+) line.

Fortunately my Aironet 350 and 7940 IP phone must have diode protection to prevent damage from a reverse polarity connection, so I was lucky there!

I'm just going to make up a dedicated cable which will crossover pins 4&5 with pins 7&8. Problem solved!!

Hope this will help other people out.

RG

POE - Aironet 350 / 7940 IP Phone?

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