Cisco power injector compatibility issue

at Cisco Catalyst Switch, if you using old power injector(before AIR-PWRINJ3), you can suffer wireless signal down.

but, you can overcome using this command.

ap(config)#power inline negotiation injector installed
 A power-injector must be installed on port: WS-C2960S-48FPS-L(Gig 1/0/27)(MAC=8cb6.4ff2.d39b)


ap(config)#power inline negotiation injector 8cb6.4ff2.d39b

MAC address can changable. and you must connect AP to Switch directly.