Do not decide that an existing security camera is PoE simply because it has an Ethernet cable. The reliable answer comes from two matching facts: the exact camera specification lists a recognized PoE standard, and the installed cable traces back to equipment that is actually supplying power. An RJ45 connector proves a network connection; it does not identify the power source. This distinction matters before replacing a camera, reusing cable, or buying a new NVR or switch. A mistaken assumption can leave a new camera without power, send the wrong voltage to older equipment, or turn a simple replacement into an unplanned rewiring project.
Begin at the camera, but treat the connectors as clues
Inspect the camera pigtail or connection compartment without disturbing weather seals or exposed wiring. A single connected Ethernet cable with no separate power lead in use suggests PoE, especially when the camera has no nearby outlet. It is still only a clue. A hidden injector, splitter, Ethernet-over-coax adapter, or proprietary passive power device may exist elsewhere in the route. A camera can also have both an RJ45 port and a round DC input. If the DC input is connected to a power supply, the camera is not currently being powered through Ethernet, even if that model supports PoE as an alternative. Photograph the connector arrangement and label the camera location before following the cable.
Trace the cable to the device that supplies power
Follow the Ethernet run to its other end. It may terminate at an NVR port marked PoE, a PoE network switch, or a small midspan injector with separate data-in and power-plus-data ports. Cisco describes the source as power sourcing equipment, or PSE, and the camera as the powered device, or PD. The PSE label, model specification, and port status are stronger evidence than cable appearance. On a managed switch or some PoE NVRs, the port page may show that a powered device is detected and report allocated or measured wattage. Record the port number and status while the camera is operating. A link light alone is insufficient because it confirms a network link, not necessarily PoE delivery. If the cable ends at an ordinary non-PoE switch, look for a separate injector or local power supply. Do not assume that every switch with Ethernet ports provides power. Conversely, a hidden injector can make a camera appear to be powered by an ordinary switch when power is being added between the switch and camera.
The exact model specification settles what the camera can accept
Copy the complete model number, including its suffix, from the device label or management interface. Find the matching manufacturer datasheet and look under Power, General, or Network for terms such as IEEE 802.3af, 802.3at, 802.3bt, PoE, PoE+, or a PoE class. Also record any separate DC or AC input. Similar housings and nearly identical model names can have different power requirements. The DS-2CD2043G2-IU 4MP AcuSense Bullet Camera with Mic illustrates why both paths must be recorded. Its published specification lists 12 VDC input and IEEE 802.3af Class 3 PoE. That means the model can accept either supported method; seeing its unused DC connector would not prove how an installed unit is powered. It is not a drop-in replacement for a coax camera, and its video, lens, audio, and NVR compatibility still require separate checks.
Use live port data or a PoE tester when the route is uncertain
When labels are missing or cables disappear into walls, an appropriate PoE tester can be placed in the Ethernet path by a qualified person to identify delivered power and, depending on the tool, the detected standard or pairs in use. For a business-critical view, plan the interruption and confirm recording resumes afterward. A tester identifies the power path; it does not prove that a proposed replacement is compatible with the recorder. Standard-compliant PoE equipment detects a compatible powered device before normal power is supplied. That safeguard should not be extended to unidentified passive injectors, which may place voltage on the cable without the same negotiation. Never connect an unknown legacy camera to a passive source merely to see whether it starts. Verify the injector model, output, polarity, and the camera specification first. An unplugged cable can also produce a false conclusion. If the camera has failed, port power may be disabled, the switch may be offline, or the cable may be damaged. In that case, use the camera specification and the source-equipment model as the primary evidence rather than treating a zero reading as proof that the installation is not PoE.
Separate PoE from coax power and document the upgrade boundary
A BNC coax connection usually points to an analog or HD-over-coax camera, not a standard PoE network camera. Power over Coax, often abbreviated PoC, is a different technology. Adapters can also carry network traffic or power across existing coax, so identify every device at both ends before deciding the cable itself can connect directly to a new PoE camera. Finish with a one-page camera schedule: location, full model, connector type, cable destination, power source model, switch or NVR port, listed PoE standard, and any alternative power input. Mark uncertain rows instead of guessing. Reuse the existing infrastructure only when the camera specification, power source, cable path, and recorder connection all agree. If one of those four items remains unknown, resolve it before ordering replacements or a new PoE switch.