Power over Ethernet or PoE describes any of several standard or ad-hoc systems which pass electric power along with data on twisted pair Ethernet cabling. This allows a single cable to provide both data connection and electric power to devices such as wireless access points, IP cameras, and VoIP phones.
A. Power over Ethernet Theory
There are 4 signal pairs in typical CAT.5 cables. For 10BASE-T and 100BASE-TX, only two of the four signal pairs in typical Cat 5 cable are used. But it makes full use of all four twisted pairs in a typical Cat 5 cable in standard of IEEE802.3af. The positive voltage runs along pins 4 and 5, and the negative along pins 7 and 8. When data pins supply power, the DC power is added to the middle point of the transmission transformer without affecting the data transmission.In this way the pins 1, 2 and pins 3, 6 can be used to any polarity.
B. Advantages of PoE Switch Used in CCTV Monitoring.
1.Convenient for wiring.
It is convenient to wiring using PoE technology, with transmission distance of 100 meters. Especially in HD monitoring system, the PoE technology simplifies the deployment and saves the cost effectively.
2. High compatibility.
Support both IEEE802.3af/at, with End-span and mid-span, it reduces cable wastage effectively. What’s more, it provides higher power at farther distance, and is suit for PoE settings of common cameras in current market.
3. Multiple-way of heat dissipation, extend the service life.
Compared with common Ethernet switches, PoE switches have higher power consumption and higher chip heat generation. Therefore, excellent cooling scheme is an important guarantee for the stability of PoE switches. Many PoE switches adopt multiple heat dissipation design, which can improve product stability and extend the service life.
4. Strong Performance of Data Processing, Ensue the Stable Operation of Network
The switching capacity of a switch is the maximum amount of data that can be consumed between the interface processor/ interface card and data bus. It stands for the data switching ability. The higher of switching capacity is, the greater the capacity of processing data could be, but designing cost would be higher accordingly.
C. Comparison Between PoE and Legacy Power Line
Although legacy power line is good, it cannot adapt to the rapid development of network monitoring. With further promote of the safe city construction, you can find surveillance cameras all around, such as road, shopping mall, hotel, KTV, supermarket, school, etc., Due to the huge amount of cameras, it is troublesome of how to supply a stable power to them. While, it is easy to solve your troubles with the PoE switch, which providing both data and power transmission through one cable for a monitoring system. Without wiring limited, it is flexible and eco-friendly, and saves the labour cost. Meanwhile, without the high voltage deployment, it is safe, and its maintenance and management could be simply as well.
D. Application of PoE Switch
Generally, it only needs a set or several sets of PoE switch to provide a stable power in a small-scale monitoring system. While, in medium/ large scale monitoring system, it adopts cascade connection scheme of network switch, namely, access layer switches, aggregation layer switches and core layer switches.
No matter what scale of the system is, as long as selecting the proper PoE switch, it could supply a stable power, and provide a fluent video stream transmission with the high quality.