How Does a Phone Circuit Work?

Phone circuits are made up of a positive, or tip end, and a negative, or ring end.

Telephone circuits are dedicated connections used to transmit voice or data information. Phone circuits rely on a tip-and-ring operation, which form the two sides of a phone's circuit.

Tip

The tip is the positive, or ground, side of the phone circuit. Ground refers to the electrical circuit that uses the earth or ground as a return path or direct connection. The tip side of the phone circuit typically connects to the telephone company.

Ring

The ring is the negative, or battery, side of the phone circuit. Batteries use electrochemical cells to transform chemical energy into electrical energy that is distributed via the circuit. An electrochemical cell facilitates chemical reactions through electrical energy. The ring side carries -48 volts of direct current, or DC voltage, when idle.

Combination

Combining the tip-and-ring line connections creates a phone circuit. Activating, or "ringing," the phone in an incoming call requires about 90 volts of AC, or alternating current, to be sent, or superimposed, over the direct current voltage at the ring side of the circuit.

References

• TopBits.com: Tip and Ring
• "Automatic Telephone Systems ; House Telephones ; Testing of Telephone Circuits ; Telephone-Line Construction ; Telephone Cables ; Power Equipment"; International Correspondence Schools; 2010

Resources

• "Understanding Telephone Electronics"; Joseph Carr, Steve Winder, and Stephen Bigelow; 2001