How Does a Telephone Jack Work?

The Jack

The telephone jack is nothing more than a connection system for telephone equipment. The jack itself is a small rectangular piece of plastic that is mounted to the wall and connected to the telephone plug. A telephone connects to the jack into the plug, and through this plug telephone service is received.

Connections

The telephone plug connects red and green wires to each jack in your home, and then to a telephone to the network box, usually located on the outside of the house or building. The green wire is common and the red wire supplies the voltage needed when calls are incoming or outgoing. The network box connects to an entrance bridge, usually near the road, with a pair of copper wires.

Switchboard

The entrance bridge connects to the local telephone network, and all calls are filtered through an electronic switchboard. When a call is made the switch can detect that the loop through the network has been completed and it sends out a dial tone. The dial tone is the signal that lets the user know that both the switch and phone are working. The switch lets you know when you have an incoming call by sending out a ringtone through the lines with a frequency of 20 Hz. The voltage used in a home depends on a variety of factors such as the loop length (how far is the call coming from), the number of ringers in a home, and the length of the ring.