A telephone is not much use on its own. Its value comes from the network around it. Between 1877 and 1900 the telephone went from a novelty connecting two rooms to a service connecting whole cities.
A louder transmitter¶
Bell's original electromagnetic transmitter produced a very weak signal. In 1877–78, Thomas Edison and Emile Berliner (among others) developed the carbon transmitter. Sound waves press a diaphragm against loosely packed carbon granules. That changes their electrical resistance, which in turn changes a current supplied by a battery. The phone was no longer generating the signal from the voice's own energy. It was controlling a much stronger current, so the result was far louder and clearer.
Carbon microphones remained standard in telephones for about a century, until electret and other electronic microphones replaced them.
Switchboards and operators¶
Early telephones were sold in pairs and wired directly to each other. With dozens of subscribers, connecting every pair directly was impossible: n phones need n(n−1)/2 wires. The solution was a central hub, the exchange.
- The first commercial exchange opened in New Haven, Connecticut, in 1878, with 21 subscribers.
- Each subscriber's line ended at a jack on a switchboard. An operator answered an incoming signal, asked for the wanted party, and connected the two lines with a patch cord.
- The first operators were teenage boys hired from the telegraph business. They were widely considered rude and unreliable. Emma Nutt, hired in Boston in 1878, is generally named as the first woman operator. Within a few years the job was almost entirely held by women, and stayed that way for most of a century.
This star topology is the same basic shape as a network switch or hub today: every endpoint connects to a central point that forwards traffic.
Power from the central office¶
Early phones had their own batteries for the transmitter and a hand-cranked magneto to signal the operator ("ringing up" the exchange). Common battery systems, developed in the 1890s, moved the power to the exchange, which fed DC down the line to every phone. Lifting the handset was enough to draw current and light a lamp on the operator's board.
That design lasted. A copper landline is powered by the central office at roughly 48 V DC, which is why it keeps working during a home power outage. A fibre or VoIP phone depends on powered equipment in the home.
The Bell Telephone Company of Canada¶
The Bell Telephone Company was founded in the U.S. in 1877. In Canada, the Bell Telephone Company of Canada was incorporated by an Act of Parliament in 1880. It is the direct ancestor of today's Bell Canada.
In 1895 it spun off its equipment manufacturing as the Northern Electric and Manufacturing Company, later Northern Electric, then Northern Telecom, and finally Nortel. Northern Electric built the telephones Canadians rented from Bell for most of the 20th century. Nortel later built much of the digital switching equipment in North America (see The digital network).