Analog transmission works fine for voice transmission on the local loop and the existing copper pairs coming into our homes will exist in some parts of the United States for a number of years. Several companies have been working towards converting the copper twisted pair local loop to fiber. In addition several cable television companies are now offering dial tone to their customers.
Let’s continue our focus on the telcos and look at what happens to our analog voice transmission when it gets to the telephone company Central Office (CO).
Local Loop and CO
Our analog voice signal is converted to a digital signal by a device called a CODEC (short for Coder/Decoder) and is then multiplexed, or combined, with other converted analog signals coming from other telephones or analog modems being served by the same CO. Once multiplexed, the calls are then sent out of the CO along their way on a higher bandwidth transmission medium such as fiber or microwave.
I'll write about CODECs in my next post and multiplexing in a future post.