Mitel MiVOICE BUSINESS, Engineering Manualline

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Power
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Once the “signature” or impedance has been detected, the voltage is increased and current
draw is monitored. The amount of current drawn allows the PSE to classify the device for Power
over Ethernet requirements. Classification is an optional part of the standard and allows the
end device to “inform” the PSE of its power requirements. It is only performed on initial power up.
• Class 0 is the default. Devices that do not support the optional classification will default to
this setting. Class 0 requests the PSE to provide 15.4 Watts of power.
• Class 1 requests the PSE to provide a maximum of 4 Watts.
• Class 2 requests the PSE to provide a maximum of 7 Watts.
• Class 3 requests the PSE to provide 15.4 Watts (like Class 0), however, the PD will always
draw at least 7 Watts or more.
Power required for MiVoice IP Phones is fairly constant whether in use or sitting idle. Very loud
ringer and hands-free settings can draw more power than normal. Also, additional devices
connected to the IP Phone such as a PKM, a LIM and a Conference Unit increase the power
required by the IP phone. For details on optional device power requirements refer to “Power
Requirements for 5220 IP Phone Optional Accessories” on page 112.
Table 35, “802.3af Power Class Advertisements,” on page 106 can be used to determine which
Class a particular phone advertises.
3300 CXI/CXI II ICP 802.3AF POWER OVER ETHERNET CAPABILITIES
The CXi/CXi II includes a 16-port managed Layer 2 Ethernet switch. The 16 Ethernet ports
comply with the 802.3af Power over Ethernet (PoE) specification, which enables them to deliver
power to IP phones and other Ethernet devices over Category 3 or 5 cabling.
The CXi/CXi II controller’s Layer 2 switch can provide 100 Watts of power to 802.3af-compatible
devices according to the following general rules:
• Depending on the phone and option power requirements, up to 16 IP Phones could be
supported.
• Up to four PKMs (PKM12 or PKM48) are supported on Dual Mode IP Phones. Only one
PKM can be attached to a set. Multiple PKMs on a set require an AC adapter.
• Conference units require an AC adapter.
• Class 1, 2, and 3 devices receive 4, 7, and 13 Watts, respectively. Unclassified (Class 0)
devices are budgeted 7.5 Watts by the PoE subsystem, but can receive up to 13 Watts.
• Port 1 has the highest priority, port 16 the lowest.
The CXi and the CXi II PoE sub-sections are functionally identical with one exception, the
mechanism used by the controller to determine the IP phone power requirements is different.
• The CXi uses the IEEE 802.3af power advertisements transmitted from the phones to
determine how much current the phones will draw.
• The CXi II measures the actual current that the phones are drawing.
In both cases a maximum of 100 Watts of PoE power is enforced.
If the maximum system power budget of 100 watts is exceeded, power will be turned off to the
ports, starting with port 16 and ending with port 1, until less than 100 Watts is being consumed.