Lantronix
SESPM1040-541-LT-xx Install Guide
33772 Rev. F
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53
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64
Mode A vs. Mode B
Alternative A, also known as Mode A, uses the data pairs of an Ethernet link to deliver power. Data Pairs include
pins 1,2 and 3,6. PSEs using Mode A supply a positive voltage to pins 1 and 2. Alternative B, also known as Mode
B, uses the spare pairs to deliver power. Spare Pairs include pins 4,5 and 7,8.
802.3af/at Standard “compliant” vs “compatible” PDs
Knowing the difference between PoE “compliant” devices and “compatible” devices can help avoid
interoperability and connectivity issues. Compliant and compatible PoE devices are not held to the same
802.3af/at standard:
•
802.3af/at “compliant” PDs fulfill the IEEE strict requirement to support both Mode A and Mode B power
modes.
•
802.3af/at “compatible” PDs typically can provide power using only Mode B.
Typical PD Power Requirements
•
1.8 Watts: Lantronix’ M/GE-ISW-SFP-01-PD (Class 1 Powered Device (0.44 Watts – 3.84 Watts).
•
13W: IP Camera, VoIP Phone, Wireless Access Point, Networked Audio.
•
30W: IP Telephone, WiMAX Access Point, PTZ Camera, Remote Computer Terminal.
•
60W : Door Access System, Video Phone, Thin Client.
•
100W: Digital Signage Display, Point-of-Sale System, LCD TV, Computer Monitor.
•
200W: Larger TV, Larger Display, Larger Monitor, Laptop.
After eliminating basic network factors, ask your PD vendor for the PD’s power supply mode and polarities
supported and exact power consumption.
Mixing POE and Non-POE Devices
You can mix POE and non-POE devices on the same POE switch (i.e., you can put PCs on the same POE switch as
a WAP or an IP camera). The PSE (your switch) will only send power if requested by the PD.
Legacy PD Detection / Capacitor Detection
Legacy PDs refers to powered devices manufactured before the IEEE standard was finalized and do not have the
expected PD signature required by the PSE’s detection signal. Such PDs usually feature large capacitance as the
detection signature that does not completely comply with the 802.3af specs. By enabling this option, the switch
will probe for legacy PDs and if a legacy PD is detected, the switch will provide power to the PD.