Introduction to Data Communications
Previous 16. Telephone Networks Next

16. Telephone Networks

The telephone network consists of your phone at home, that is connected by the Local Loop to the Central Office which is connected to a Hierarchical Phone Network. Worldwide there are over 300 million (300,000,000) telephones - 98% of them interconnected.

16a. POTS - Plain Old Telephone Set

The POTS or Plain Old Telephone Set consists of 5 sections:

  1. Ringer Unit
  2. Hook Switch
  3. Dialer Unit
  4. Hybrid/Speech Network
  5. Hand Set

The connection to the CO (Central Office) is with only 2 wires: Tip and Ring. This connection is called the Local Loop.

The Tip is +ve and coloured green.. The Ring is -ve and coloured Red. If you look at a phone jack in your house, you will see that it is wired for 4 wires: Red, Green, Black and Yellow. Black and Yellow are not normally used.

The black and yellow wires can be used for a second telephone line or they can be used for running a Network Physical layer protocol called Phonenet by Farralon. Phonenet uses the Black and Yellow for Network communications. It is for use with Appletalk and is a replacement for Localtalk. It runs at the Localtalk speed of 230 Kbps which is reasonable for small networks.

Introduction to Data Communications
Previous Table of Contents Next

Copyright Eugene Blanchard Jan 1998, January 2007