A network technician is troubleshooting an IP surveillance camera that repeatedly reboots whenever its high-power infrared illuminators activate at night. The camera is powered via Power over Ethernet (PoE) over an 85-meter Category 6 UTP cabling drop. A basic wiremapper confirms correct T568B pinout continuity with no opens or shorts. Which TWO of the following diagnostic findings or procedures are most accurate for identifying and resolving this physical cabling issue?
- High DC resistance resulting from a poor RJ-45 crimp or oxidized IDC punch-down point causes excessive voltage drop when current draw increases.Cevap
- Using a cable certifier to measure DC loop resistance and resistance unbalance across the individual conductor pairs.Cevap
- CUsing a basic continuity wiremapper to measure signal attenuation and high-frequency crosstalk under peak power load.
- DDeploying an Optical Power Meter (OPM) to measure signal loss along the copper conductor run.
Cevap
The issue is caused by high DC resistance on the copper conductors (such as a poor crimp or oxidized punch-down), which leads to excessive voltage drop when the camera's current consumption spikes. To properly diagnose this physical layer issue, a cable certifier must be used to measure DC loop resistance and resistance unbalance.
Power over Ethernet (PoE) delivery over long copper runs relies on low DC resistance across wire pairs. High resistance caused by loose IDC terminations or poor crimps creates an excessive voltage drop under heavy current load (such as when IR LEDs engage). Because basic wiremappers only verify 1-to-1 pin connectivity, a cable certifier capable of testing DC loop resistance and unbalance is required to detect high-resistance faults.
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DC Loop Resistance and Voltage Drop in PoE Cabling