PoE security cameras: how one cable carries power and video

Power over Ethernet sends power to a device over the same cabling that carries its network traffic. Axis, a camera maker, describes it as a way for network cameras, wireless access points and IP phones to receive both power and data over existing network cabling, with the switch acting as a central power source.

The camera is the powered device. The equipment at the other end of the cable that supplies the power can be a PoE switch, a small box called an injector, or a recorder that has PoE ports built in.

PoE works with network (IP) cameras. Analog cameras connect to a DVR with coaxial cable, which is a different kind of system. Hikvision's support site notes that an NVR cannot take analog cameras directly. Our DVR vs NVR guide helps you tell which one you have.

• One cable per camera, so there is less to run and less to fix.
• No power outlet needed near the camera. That helps on ceilings, outside walls and in yards.
• Power comes from one place. If that switch or recorder is on a battery backup, the cameras it powers can keep running for as long as the battery lasts.

Already have cameras and a recorder? Try Foreman free for 7 days, no card

Many network recorders (NVRs) have a row of PoE ports on the back. A separate PoE switch is another box. Both power cameras, and they behave differently.

• PoE ports on the recorder. You plug a camera straight into a port on the recorder, and the recorder powers it. Hikvision's support article says plug-and-play works only when the camera is connected directly to a PoE port on the NVR. Dahua's manual says cameras connected to the PoE ports on the back of an NVR are isolated from the outside world and cannot be accessed directly. That is a security benefit. It also means other computers reach those cameras through the recorder, not one by one.
• A PoE switch. Cameras plug into the switch, and the switch connects to your network and to the recorder. Hikvision describes adding such cameras to the NVR by entering each camera's address, user name and password. A switch is also how you add more cameras than the recorder has PoE ports for. Hikvision's answer to that question is to connect the PoE switch to the NVR's network port.

Three IEEE standards define how much power a PoE source can give. The Ethernet Alliance, the industry group for Ethernet, publishes the levels. Newer sources work with older devices. The one limit is that a device that needs more power than the source gives will not get its full power.

The camera always receives less than the source sends, because some power is lost along the cable.

• 802.3af, also called PoE or Type 1: up to 15.4 watts from the source, about 13 watts at the camera. Many fixed cameras fit inside this.
• 802.3at, also called PoE+ or Type 2: up to 30 watts from the source, 25.5 watts at the camera. Cameras with a built-in heater are an example of why a camera may need more.
• 802.3bt, Type 3 and Type 4: up to 60 and 90 watts from the source, 51 and 71.3 watts at the device. For demanding cameras and other high-power equipment.

A PoE switch or recorder has a limit per port and a total budget for all ports together. Axis explains that the per-port maximum is separate from the total. What matters is that the total is more than all your cameras draw at once.

Axis gives a simple example. Six cameras that each draw up to 7 watts need a switch with at least 42 watts available for PoE, because 6 times 7 is 42.

Some cameras list two power figures. Axis notes that a camera may need more power when extra equipment such as a heater is included, so a datasheet can show one number for the camera alone and a higher one with the heater. Check the total PoE power on your recorder's or switch's datasheet, add up the maximum draw of your cameras, and leave a margin. Axis recommends keeping a margin.

One run of network cable between the power source and the camera is limited to 100 meters (about 328 feet). Both Axis and NETGEAR give this figure, and NETGEAR says it applies to 802.3af, 802.3at and 802.3bt. The 100 meters is the total, patch cables included. Axis suggests as a rule of thumb 90 meters for the fixed run and 10 meters for the patch cables.

The cable matters too. Axis recommends Cat 5e or Cat 6, and warns that a poorly crimped connector can stop PoE from working properly. NETGEAR advises Cat 6 for the highest-power standard, 802.3bt, with Cat 5e as the minimum.

Outdoors, Axis says to use shielded cable (STP) with a properly grounded power source, and to run outdoor network cable in conduit.

To go past 100 meters, NETGEAR says repeaters or switches can extend the signal, so a powered switch partway along the run is the standard answer. Some makers also sell long-range PoE as their own feature. Dahua, for example, lists NVR models with ePoE ports that support 300 meters at 100 Mbps. That is the maker's feature and not part of the standard, so check that your camera supports it.

Standard PoE (802.3af, 802.3at, 802.3bt) checks that a device is PoE-ready before it sends power. Passive PoE is a non-standard kind that does not. NETGEAR says passive PoE does not do a handshake, so it is extremely important to know what voltage your device needs before you plug in, because the wrong voltage may cause permanent damage. It gives 24 V cameras and antennas as common examples.

So read the datasheet. If it says 802.3af or 802.3at, it is standard. If it names only a voltage, such as 24 V, and no 802.3 standard, treat it as passive, use the power supply that came with it, and ask the maker before you connect it to a standard PoE port.

Look in four places.

• The camera. A network camera has a network cable with an RJ45 plug. If that is the only cable and there is no power adapter at the camera, the cable is carrying power too. If you also see a power plug or power cable at the camera, it is powered separately.
• The label or datasheet. Look for PoE, IEEE 802.3af or 802.3at. Axis datasheets, for example, show the power line as PoE with the standard named, sometimes next to a DC voltage range.
• The recorder. Look at the back for a row of network ports marked PoE. The datasheet lists the number of PoE ports.
• A switch or injector. A switch labelled PoE, PoE+ or PoE++ powers cameras. An injector is a small box with its own power adapter, sitting between a switch and a camera.
• A coaxial cable with a round BNC plug usually means an analog camera on a DVR. That is not PoE.
• A quick test. Unplug the camera's network cable at the recorder or switch. If the camera goes dead, that cable was powering it. Plug it back in straight away, because that camera stops recording while it is unplugged. If you are not sure, ask your installer.

• The run is longer than 100 meters, or the cable is damaged.
• A connector is badly crimped. Axis says this can stop PoE from working properly.
• The switch or recorder has run out of PoE budget because all the ports together ask for more than it has.
• The camera needs a higher standard than the source gives. A source that gives 15.4 watts cannot fully power a camera that needs 25.5.
• The port is switched off in the recorder's or switch's settings.
• The camera uses passive PoE and the source is standard PoE, or the other way round.

PoE decides how a camera gets power. It makes no difference to software that reads the video. Our software connects to your recorder or cameras over the network, and it does not care whether a camera is PoE. If your cameras sit on the recorder's PoE ports, it connects to the recorder.

It runs on a Windows computer at your site, works with the cameras and recorders you already have, including Hikvision, Dahua, CP Plus, TVT, Uniview, Axis, Hanwha and any camera or recorder that supports RTSP or ONVIF, and installs in about 60 seconds. Four things are standard on every site: smoke and fire, people after hours in zones you mark, a covered camera, and a warning when a camera goes offline. A second, larger model checks every event before you are alerted, and the alert is a photo on WhatsApp, Telegram or the Foreman app while it is still happening. Your recordings stay on site, and we never train on your footage.