Difference Between Active vs. Passive PoE

Difference Between Active vs. Passive PoE 

Power over Ethernet or PoE for short can be a new and potentially confusing term to a lot of people searching for security cameras. PoE connectivity simplifies cabling needed to connect a device by allowing power and data delivery over a single network cable such as CAT5e or CAT6. It makes it easy to connect devices such as IP security cameras, or office phones; a separate power supply or electrical outlet for each device is not needed. However, it is important to know the nuances about PoE equipment to avoid damaging your equipment. There are two types of PoE connections - active and passive. While one may think active is with power and passive is without power, that's not correct.

Active Power over Ethernet (PoE) uses an automatic negotiation handshake to safely deliver dynamic power levels based on device requirements, whereas passive PoE sends a constant, fixed voltage without any communication or safety check.

Active PoE

802.3af/at Compliant PoE - Good for IP cameras

Active PoE means that a device is rated to be 802.3af or 802.3at compliant. These are regulated specifications that require a device and power supply to do a “handshake” or verification. The PoE power supply tests the connection to the device and ensures that the power is compatible. If it isn’t, then the device simply will not power up, preventing any potential damage.

Active PoE Standards (IEEE 802.3)

The IEEE defines several Active PoE standards that determine how much power can safely be delivered.

Standard	Name	Max Power	Voltage Range
802.3af	PoE	Up to 15.5W	44–57V DC
802.3at	PoE+	Up to 30W	50–57V DC
802.3bt	PoE++	60–90W	52–57V DC

Passive PoE

Raw unnegotiated power - Bad for IP cameras

Passive PoE refers to any device that does not follow the 802.3af or 802.3at specifications. Passive PoE does not do any sort of power check so it simply supplies power regardless of what it is plugged into. This can damage any equipment not rated to accept the passive PoE power input. It is extremely important to understand the requirements and specifications of your equipment before plugging anything in.

Unfortunately, we see it too often that a customer damages their newly purchased IP security cameras when using a PoE switch such as a Unifi Switch that can output Passive PoE Power. If you choose to use your own PoE switch, we recommend use of reputable manufacturers such as Cisco, Netgear, or TP-Link that manufacture 802.3af/at compliant PoE hardware.

Calculating Passive PoE Power

If a device requires 12W and supports 12–30V, and you are using a 24V Passive PoE injector, you will need at least 0.5A to meet the power requirement:

24V x 0.5A = 12W.

Practical Limits for Passive PoE

·        24V Systems: Typically limited to about 50 metres due to higher voltage drop at lower voltages.

·        48V Systems: More efficient for longer runs, as higher voltage reduces the current needed for the same power, thereby minimizing heat loss (I²R).

·        Wiring: Passive PoE often uses Mode B, sending power over the "spare" pairs: pins 4/5 (+) and pins 7/8 (-)

Now question is How to access a PoE Security Camera from a Computer

We’re often asked how to modify an IP camera’s video settings once you already have it up and running on your NVR. This process can be difficult without any knowledge of computer networking or setting up a standalone IP camera. In this article we explain the technical details of taking a camera from the back of your NVR and connecting to it with either a direct connection or through your network.

The first steps include understanding how a camera and PoE NVR work together, noting the IP address the camera is configured to and finally physically removing the camera from the NVR.

After having a grasp on the basics and noting the IP address of your camera you can then proceed to the next steps. There are two ways that you can connect to a camera’s web interface:

·       The first is through a direct connection into your Windows desktop or laptop that has an ethernet port.

·       The second involves going over your computer network by configuring the camera to communicate on the network.

Be sure to note the IP address of the camera before disconnecting it from the NVR, you will need it later.

A) Direct connection between IP camera and Computer

The easiest way to access an IP camera is by connecting to it directly from a computer. This method requires you have the following:

1.   The IP address of your camera from the NVR registration page

2.   PoE Injector or 12VDC 1A Power Adapter. It is very important to use a CCTV Camera World approved device or you risk frying the camera due to incorrect voltage

3.   Two Ethernet cables (one if using a power adapter)

4.   Windows 11 pro based PC

1. Use a PoE injector to supply power and data

A PoE injector will have two ports, one labeled for PoE or P+D/Out (power and data) and one labeled LAN or Data/In. Connect the PoE injector to a power outlet. Connect an ethernet cable from your PC's network port to the Data/In on the PoE injector. Connect a second ethernet cable from the network camera's RJ45 network jack to the port labeled PoE or P+D/Out. To check if everything is connected properly refer to the lights on the PoE injector and the port on your computer. If you do not see any indication lights you may have a bad cable or do not have the wires connected properly.

2. Use a 12VDC 1A power adapter

A correct power adapter will have a label stating it is 12VDC 1000mA. Connect an ethernet cable from the camera directly to your computer’s ethernet port. A good way to check if the camera is receiving power and communicating with your computer is to look at the lights on your computer’s port. If you have no lights it is important to test that your cable and power supply work with another device.

3. Configure your PC's network port to communicate with the camera

For your computer to "speak" to your camera, you need to set its network port to the same IP address scheme as the camera. Before we disconnected the camera from the back of the NVR, we noted what the IP address of the camera was.

Login to your Windows PC, change your computer's ethernet adapter to communicate with the camera. Use the Network & Internet settings which contains an Ethernet section. Using the change adapter settings set an IP address for your computer that matches the network for the camera. If you do not know how to do this refer to the video above for this step.

4. Test the connection with the Ping command

After powering the camera and configuring your computer to talk with it, it is good practice to test the connection using the Ping command. Simply open the Command Prompt and type Ping with the address of the camera. In our case we used the following command: ping 10.1.1.65 -t press enter key.

5. Access the camera using Internet Explorer

It is important to use Internet Explorer as it is the most compatible browser for accessing security cameras. Type the IP address of your camera into the address bar in Internet Explorer. Some cameras may require initialization and it is recommended to uncheck the Easy4IP and auto-update options when proceeding through the prompts. The password can be admin, or may be printed on the label found on the box of the camera. Note: the customer is responsible for any password change beyond the defaults. There is no master reset password.

After successfully logging into the camera you need to install a plugin to view the camera. Click the link in the center of the page to download the plugin. Make sure to Run and do not save the plugin download. Internet Explorer will prompt you to allow the plugin to run. Once the plugin is installed, you will be required to log back into the camera. You should now see video from your camera and can modify the settings of the camera in the Setting tab within your browser. Make sure when you are done modifying your camera(s) that you change your network settings back to “Obtain IP address automatically” in your network settings, this is demonstrated in the video above.

B) Accessing the camera over your network

Besides direct connection to a computer, the other method to connect to a PoE security camera is over the network. This method requires the following pre-requisites:

1.   A home or business network with router

2.   Windows PC with ConfigTool installed

3.   PoE Injector or 12VDC 1A power adapter

4.   A network cable to connect to your router

5.   The IP address of your camera

1. Power the camera

You can use a PoE injector or 12V DC 1amp power adapter to power the camera and connect to your network router or switch. The process is simple. It is very important to use a CCTV Camera World approved device or you risk frying the camera due to incorrect voltage.

2. Connect the camera to your network router

Instead of connecting the camera directly to your computer, you will connect it to your network router so the computer can communicate with the camera over the network. When following this guide, it is important to connect the camera and computer to the same router or switch. We suggest using a hardwired connection between the computer and the router to prevent a situation where your WiFi network is different from the wired network. If you are knowledgeable about your network setup, feel free to use a WiFi laptop.

3. Use the ConfigTool to find the camera and change its IP address

Using the ConfigTool to find the camera on your network is fairly easy. It is imperative that you turn off any firewall or antivirus program on your computer that may prevent the program from sniffing your network.

4. Access the camera's web interface using Internet Explorer

The steps are similar to method A because the web interface will be the same regardless of how you connect to the camera.

Method for Identifying a PoE Power Supply Failure Caused by High Network Cable Resistance

If network cables can be removed from the switch at the local site, use below method to measure the resistance.

·        Measurement tool: Multimeter

·        Measurement contents and procedure: Use the multimeter to measure the DC resistance of each cable wire and take down the measured values as R1, R2,…R8.

·        Measurement results:

Network cable resistance:

R = (R1 + R2 + R3 + R6)/4 (when the switch uses the wires 1, 2, 3, and 6 to supply power.)

Or:

R = (R4 + R5 + R7 + R8)/4 (when the switch uses the wires 4, 5, 7, and 8 to supply power.)

Usually, the AC and PoE switch use wires 1, 2, 3, and 6 for power supply, and the PoE adapter uses wires 4, 5, 7, and 8 for power supply.

Key Takeaways

The primary difference between Active and Passive Power over Ethernet (PoE) is how they deliver power: Active PoE communicates with a device to ensure it is safe to power, while Passive PoE sends electricity immediately without checking compatibility.

Active PoE (The "Smart" Choice)

Active PoE is the industry standard for most modern business networks.

·        Intelligent Handshake: The power source (PSE) sends a low-voltage signal to detect if the connected device is PoE-compatible and determines exactly how much power it needs.

·        Protection: If you plug in a laptop or a non-PoE device, the switch detects it and sends only data, preventing electrical damage.

·        Common Standards:

o   PoE (802.3af): Up to 15.4W per port.

o   PoE+ (802.3at): Up to 30W per port.

o   PoE++ (802.3bt): Up to 60W or 100W for high-power devices.

Passive PoE (The "Always-On" Choice)

Passive PoE is common in specific setups like outdoor wireless bridges or legacy equipment.

·        No Communication: It does not check the device's needs; it simply pushes a fixed voltage over specific pins in the Ethernet cable.

·        High Risk: If you plug a device into a passive port that doesn't match its required voltage (e.g., 48V into a 24V device), it can cause permanent electrical failure.

·        Manual Matching: You must manually verify that your injector or switch matches the exact voltage and pinout required by your device.

Which should you choose?

·        Choose Active PoE for almost all standard office or home office uses (IP cameras, VoIP phones, modern Access Points) to ensure safety and future-proofing.

·        Choose Passive PoE only if you have specific legacy hardware or budget-constrained outdoor installations where you are certain the power specs match perfectly

How to Find Your Model's Requirements

1.   Check the Physical Label: Look for a sticker on the back or bottom of the device. It will often list "802.3af," "802.3at," or a specific voltage like "24V DC".

2.   Consult the Datasheet: Search for your model number + "technical specs" online. Look specifically for the "Power Method" field.

3.   Check the Box: If you still have the original packaging, the required PoE standard is usually printed on the side near the serial number.