1. SELECTION OF POE SWITCH AND POE STANDARD

There are many types of PoE switches, from megabit to gigabit, managed to unmanaged, and differences of port numbers, etc. You need a comprehensive and integrated consideration before the selection. Here we take the project that needs HD monitoring as an example.

A. Megabit VS Gigabit

Make the choice based on the combination of the number of camera channels, camera resolution, bit rate, frame rate and other parameters that the project requires.

B. How many ports should we choose.

According to the number of ports, PoE switch can be divided into 4 ports, 8 ports, 16 ports and 24 ports, etc. You can make the choice based on the monitoring equipment power, number, location, PoE power budget, price, etc.

C. PoE Standard

Most PoE switches in the market could support both IEEE 802.3af and IEEE 802.3at now, but if the PD requires power that is more than 30W, then you need an IEEE 802.3bt PoE switch.

Above is general ideas for switch selection, you can click below links to check more.

--> <Relationship Between The Number of Switch Ports And The Number Of Cameras (Part 1)

--> Relationship Between The Number of Switch Ports And The Number Of Cameras (Part 2)

2. MUST WE CHOOSE AN ACTIVE POE SWITCH RATHER THAN A PASSIVE ONE?

First, you should know the differences between them. There is a PoE control chip inside an active PoE switch. There is a function of detection before supplying power. When the device is connected, the PSE sends a signal to the network to detect whether the terminal in the network is a PoE PD device.

The passive PoE product is a strong supply type PSE, which would supply power when making the connection without any detection steps, regardless of whether the terminal is the PoE PD. It is very easy to burn access equipment.

3. HOW TO DISTINGUISH ACTIVE AND PASSIVE POE SWITCH WITH A MULTIMETER MEASUREMENT?

It is simple to distinguish active and passive PoE switch with a multimeter measurement, the method is as follows.

Test the power supply PIN of PSE, usually 1/2, 3/6 or 4/5, 7/8 of the RJ45 port, with the voltage measurement gear of the multimeter, if the voltage value is 12V/24V/48V, etc., the PSE is the passive one. In this process, the PSE does not do testing on the PD (here is a multimeter), and directly provides 48V or other voltage.

On the contrary, if the voltage is not measured and the multimeter needle jumps between 2~10V, it is an active POE PSE. because at this stage, the PSE is doing detection on the PD side (here is the multimeter), and the multimeter is not a legal PD, the PSE will not supply power and no stable voltage is generated.