Lantronix
Install Guide, SISPM1040-362-LRT and SISPM1040-384-LRT-C
30
of
51
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.
IEEE 802.3bt Power Input Ripple and Noise Specification
f
< 500 Hz
V
Noise
V
pp
0.5
500 Hz to 150 kHz
0.2
150 kHz to 500 kHz
0.15
500 kHz to 1 MHz
0.1
Troubleshooting PoE Problems
1.
Get as much detail as possible regarding the symptom, including any system messages from the PoE switch.
For example, does a PD not power up at all, or does it power up briefly and then power down?
2.
Determine if the trouble occurred on initial installation or after the PD had been working normally.
3.
If the trouble started after the PD was working, what changed? Were there any hardware or software
changes?
4.
Verify that the port is not shut down, disabled, or errored.
5.
Verify that the Ethernet cable from the PD to the switch port is good. Noncompliant cabling or powered
devices can cause a PoE port fault; use only standard-compliant cabling.
6.
Verify that the total cable length from the switch front panel to the connected PD is not more than 100
meters. Some of the power from the switch port is dissipated in the cable due to wire resistance, especially
on cables as long as 100 meters. Only the remaining power is available to the PD. The 100-meter limit for
twisted-pair Ethernet cable assumes
a)
not more than four RJ-45 connection points in the transmission path,
b)
90 meters of solid-strand Category 5 or 5e, and
c)
10 meters of flexible multistrand cable (2-to-5 meters
of multistrand Category 5 patch cords).
7.
Verify that the PSE switch power budget can power the PD. If the switch power budget is depleted,
additional PDs will not power-on when connected to a PoE port. Verify that the switch power budget
(available PoE) is not depleted before or after the PD is connected. Verify that sufficient power is available
for the PD type.
8.
Verify if non-powered Ethernet devices can establish an Ethernet link on any port and that PoE devices do
not power up on the same port.
9.
Review alarms reported previously by system messages.
10.
If a working IP Phone or WAP intermittently reloads or disconnects from inline power, verify all electrical
connections from the switch to the PD. An unreliable connection results in power interruptions and
intermittent PD operation, such as PD disconnects and reloads.
