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P a g e
PoE power supply system has unified standard, IEEE 802.3af and 802.3at. So, devices from
different manufacturers have no problem in general usage, as long as they are complied
with these standards.
PD, it is defined as powered device in the PoE Power Supply System, primarily including IP
camera, wireless AP, network VoIP phone, and other IP-based terminal equipment.
The whole process of PoE:
1. Detection:
At beginning, PSE device output a very small voltage, to detect and judge if its
linked PD is IEEE802.3af / IEEE802.3at compliant device. Only if detected that PD is a
standard compliant device, then it will go to next step.
2. PD Classification:
After detecting PDs, PSE will classify them and recognize what is the
power that PD required.
3. Power up:
When above 2 steps finished, PSE start feeding required power for PD, with
44~57VDC output voltage.
4. Power supply:
PSE provides stable 44~57V DC to PDs, and auto feeding power as
requirement of PDs. Maximum power of single PoE port for IEEE 802.3af devices: 15.4W;
Maximum power of single PoE port for IEEE 802.3at devices: 25.5W.
5. Disconnection:
If PD is disconnected or user disable PoE from management software,
PSE will quickly(300-400ms) stop powering PD.
In any moment of PSE powering PD process, PSE will stop working and then restart from
step1 if abnormal situation happens, such as PD Short circuit, power consumption is higher
than feeding power, and so on.
Summary of Contents for JTD-2886
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