Chip PC CDC01927 Class, Usage, Minimum Power, Maximum Power, Levels Output at, Levels at the

Jack PC Hardware User Manual - Training Department

Version 0506

the Jack-PC will consume only 4-6W maximum. Power may vary if demanding USB peripheral devices or dual monitors are attached to the device.

Class		Usage	Minimum Power	Maximum Power
			Levels Output at	Levels at the
			the PSE	Powered Device
0		Default	15.4W	0.44 to 12.95W
1		Optional	4.0W	0.44 to 3.84W
2		Optional	7.0W	3.84 to 6.49W
3		Optional	15.4W	6.49 to 12.95W
4		Reserved for Future	Treat as Class 0	Reserved for Future
		Use		Use: A class 4
				signature cannot be
				provided by a
				compliant powered
				device
	Table 6.2 - IEEE 802.3af PSE and Powered Device Power Classifications

Therefore for swiches with overall power limitations, Jack-PC would not usually exceed the rack limitations. If the PSE is not capable of supplying class 0 power to the Jack-PCs it may still be possible to operate at class 2 (7W maximum) although this setting is marginal and may cause random PoE power down events.

A practical example:

Lets take a rack with Catalyst 6500 series switches (240 ports):

Chip PC Jack-PC EFI-6900 typically requires 5W during normal use and 6W during full- screen video player operation.

As a comparison - Cisco IP Phone 7960G requires 7W when the phone is ringing at maximum volume and requires 5W on or off hook.

This is a significant reduction from the 15.4W maximum power allowed for within IEEE 802.3af for class 0 devices. It can be seen that PSE power requirements can be significantly reduced by budgeting for the power the device actually requires, rather than simply allocating the maximum power defined within IEEE 802.3af.

To calculate actual switch power use, we can multiply 7W by the number of ports (240) = 1680W.

30