ASR9010 : Power Shelves or Power Tray

[Maurizio Bau]

Hi Guys

i found a pdf file about Replacing Cisco ASR 9000 power supplies,but i've a dubt:Power shelves or Power Tray?

In many picture i found "power shelves" and in other i found "power tray"

What's the difference?

http://www.cisco.com/c/en/us/td/docs/routers/asr9000/hardware/installation/guide/asr9kHIGbk/asr9kIGmaintaining.html

Thanks

Regards

Maurizio