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POE ESWs and Older 79XX phones

Want to confirm if the ESW PoE switches can power pre-standard phones such as the 7940G.


Thanks

2 REPLIES
Cisco Employee

Re: POE ESWs and Older 79XX phones

Art,

     As I understand it the Pre-standard PoE vs. the 802.3af standard is the available power.  The pre-standard power supported up to 6.3 watts per port while the 802.3af standard supports up to 15.4 watts; more than double.  So the short answer to this overview is yes.

Cisco Employee

Re: POE ESWs and Older 79XX phones

There's actually more to it than that.  The circuitry used to detect a pre-standard PoE device is different from IEEE, though I've long since forgotten the details.  What this means though is that a switch needs to be specially designed to support both pre-standard PoE and IEEE PoE.  As far as I know, all of the Catalyst series switches do support both forms, while the the majority of PoE switches from the different vendors do not.    In the case of the ESW switches, it looks like you're in luck - I just doublechecked by plugging in an old 7960 to an ESW I have here and it powered up OK.

Cheers,

Dave.

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