VoIP (Voice over IP) has always fascinated me. I worked on EPABX software in 1993-94 time frame. It was all embedded world then. Smart members of our team developed the EPABX software in C programming language. It was all fun.
After so long, we have free commercial grade VoIP server softwares available, which can be installed on Linux server and used. Cheapest way to use them is by installing soft phones on PC. Other alternative is to use expensive VoIP phone instruments. These instrument come in two forms. One which takes power from Adapter and other ones expect power to be fed to them over regular Ethernet wire, which is generally used for Data communication.
I was very curious to know how power is given to these VoIP phone devices. The Ethernet cable has 4 pair of wire inside it. They are color coded too. The colors used are Green, Orange, Blue and Brown. The diagram below gives you the pin numbering of the RJ45 connector which is used to connect Ethernet cable to your PC, Laptop etc.
We can see from the diagram above, that out of 8 pins of RJ45 connector only 4 are used for Transmitting and receiving data where as remaining 4 pins ( 2 pairs) are reserved, i.e not used.
Basically these 4 pins or two pairs are used to transmit power. There are many schemes used by various vendors but most common of all, is to use pin 4 and 5 for +ve end of power source and pin 7 and 8 for the -ve end of power source.
Again, there is no specific standard on how much power is to be transferred. These pins are used to transmit from 12v to 48v depending on the need.
So these were some basics of POE ( Power over Ethernet)
Till next, take care.
After so long, we have free commercial grade VoIP server softwares available, which can be installed on Linux server and used. Cheapest way to use them is by installing soft phones on PC. Other alternative is to use expensive VoIP phone instruments. These instrument come in two forms. One which takes power from Adapter and other ones expect power to be fed to them over regular Ethernet wire, which is generally used for Data communication.
I was very curious to know how power is given to these VoIP phone devices. The Ethernet cable has 4 pair of wire inside it. They are color coded too. The colors used are Green, Orange, Blue and Brown. The diagram below gives you the pin numbering of the RJ45 connector which is used to connect Ethernet cable to your PC, Laptop etc.
We can see from the diagram above, that out of 8 pins of RJ45 connector only 4 are used for Transmitting and receiving data where as remaining 4 pins ( 2 pairs) are reserved, i.e not used.
Basically these 4 pins or two pairs are used to transmit power. There are many schemes used by various vendors but most common of all, is to use pin 4 and 5 for +ve end of power source and pin 7 and 8 for the -ve end of power source.
Again, there is no specific standard on how much power is to be transferred. These pins are used to transmit from 12v to 48v depending on the need.
So these were some basics of POE ( Power over Ethernet)
Till next, take care.
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