The lazy person's guide voice telephony-Part I

CHIPS, Winter, 2004

In today's world, most of us have three basic expectations: Flip a switch and electricity will provide power; turn on a tap and you'll get water--and lift a telephone handset and you'll get a dial tone.

Electricity, water and communications are the three main "flows" that keep modern society functioning. Over the next couple of issues, we will look at one of the main streams of communications flow: voice telephony. Originally developed in the 19th century, voice telephony became one of the killer applications of the 20th century. During the last 100 years, telephone lines have spanned the globe, linked most of the world, and served as the basis for later systems like the Internet. Its simplicity and effectiveness as a means of communication are the crowning achievements of modern technology.

Ease of use does not mean that it is simple technologically. Today, voice telephony involves a wide variety of technologies and protocols: circuit and packet switching, radiated and guided media, and analog and digital signaling, to name a few. But despite all the variations, vendors and equipment, you can pick up a phone anywhere in the world and call any other phone--if you know the number.

In recent years, telephony has been pushed out of the limelight by data and computer networking. Computer Help Desk technicians are greeted by office staff as saviors when they arrive to unstick a stuck PC. Telephone techs, on the other hand, get barely a nod as people walk past the closet where they are trying to figure out which of the 1,000 pairs of little blue and white wires on those old 66-blocks go to the phone on your desk.

So, this edition of the LPG is dedicated to all those people who make sure we can pick up a phone and talk to anyone, anywhere, in the world. We will start by looking at what it takes to connect the world with voice communications via circuit switching and guided (wired) media, the old traditional basis upon which telephony was founded. Once we have covered the basics, we will move on to wireless services and the latest trend in the voice world, voice over Internet Protocol (VoIP). But for now, and as usual when we examine any technology for the first time, let us wind up the Way Back Machine for a trip to the 19th century to see how it all started.

Telephony 101

Telephony is a system that converts the human voice to electrical impulses, transmits it and converts it to a tone that sounds like the original voice. The discovery that became the basis of the telephone came in 1831 when Englishman Michael Faraday proved that vibrations in a metal object could be converted to electrical impulses. It took another 30 years until German inventor Johann Philipp Reis built an apparatus that changed simple sounds to electricity and back again in 1861.

As with any new technology there were people willing to tell everyone else that voice telephony was impossible. In 1865, the Boston Post opined: "Well-informed people know it is impossible to transmit the voice over wires. Even if it were, it would be of no practical value." As with things like heavier-than-air flight, heart transplants and reliable overnight delivery, the pessimists were once again proved wrong.

The first practical telephones were invented by Elisha Gray and Alexander Graham Bell. Working independently, Gray and Bell both developed systems based on electromagnetic receivers with steel diaphragms. It was a tight race. Both men filed for patents at the New York patent office on February 14, 1876, but Bell got there first, beating Gray by a mere two hours. Even after the technical concept had been proven, there were still people who believed the telephone was of no practical value. In 1877, an unidentified New York financier allegedly told Bell that, "The possibility of a private home telephone system throughout the country is out of the question. Almost the entire working population of the United States would be needed to switch [install] cable."

And, in what ranks up there with the poorest business assessments ever made, there is this famous quote attributed to an 1877 Western Union memo: "This 'telephone' has too many shortcomings to be seriously considered as a means of communication. The device is inherently of no value to us." So, in response to Alexander Graham Bell's offer to sell Western Union the complete rights to the telephone for $100,000, Western Union President Carl Orton replied: "What use would this company make of an electric toy?" Once Bell Telephone negotiated rights of way for its cables and started building its network, Western Union's days as the premier communications company in the United States were numbered.

The House that Bell Built

The fundamental concept of operations for telephone systems has been a dedicated circuit connecting callers. The first phones were primitive devices, little more than a box with a hole where you both talked and listened. In Bell's demonstration model, the two units were directly connected by a single pair of wires. There was no need for a dial, as there was only one other device connected. But for the telephone to become practical commercially, you needed some way to connect callers that didn't involve setting up a different hard-wired phone for everyone you might want to call. What developed in response was the telephone exchange.