Code_ The Hidden Language of Computer Hardware and Software - Charles Petzold [19]
Morse's telegraph triumphed over other designs in part because it was tolerant of bad line conditions. If you strung a wire between a key and a sounder, it usually worked. Other telegraph systems were not quite as forgiving. But as I mentioned in the last chapter, a big problem with the telegraph lay in the resistance of long lengths of wire. Although some telegraph lines used up to 300 volts and could work over a 300-mile length, wires couldn't be extended indefinitely.
One obvious solution is to have a relay system. Every couple hundred miles or so, a person equipped with a sounder and a key could receive a message and resend it.
Now imagine that you have been hired by the telegraph company to be part of this relay system. They have put you out in the middle of nowhere between New York and California in a little hut with a table and a chair. A wire coming through the east window is connected to a sounder. Your telegraph key is connected to a battery and wire going out the west window. Your job is to receive messages originating in New York and to resend them, eventually to reach California.
At first, you prefer to receive an entire message before resending it. You write down the letters that correspond to the clicks of the sounder, and when the message is finished, you start sending it using your key. Eventually you get the knack of sending the message as you're hearing it without having to write the whole thing down. This saves time.
One day while resending a message, you look at the bar on the sounder bouncing up and down, and you look at your fingers bouncing the key up and down. You look at the sounder again and you look at the key again, and you realize that the sounder is bouncing up and down the same way the key is bouncing up and down. So you go outside and pick up a little piece of wood and you use the wood and some string to physically connect the sounder and the key:
Now it works by itself, and you can take the rest of the afternoon off and go fishing.
It's an interesting fantasy, but in reality Samuel Morse had understood the concept of this device early on. The device we've invented is called a repeater, or a relay. A relay is like a sounder in that an incoming current is used to power an electromagnet that pulls down a metal lever. The lever, however, is used as part of a switch connecting a battery to an outgoing wire. In this way, a weak incoming current is "amplified" to make a stronger outgoing current.
Drawn rather schematically, the relay looks like this:
When an incoming current triggers the electromagnet, the electromagnet pulls down a flexible strip of metal that acts like a switch to turn on an outgoing current:
So a telegraph key, a relay, and a sounder are connected more or less like this:
The relay is a remarkable device. It's a switch, surely, but a switch that's turned on and off not by human hands but by a current. You could do amazing things with such devices. You could actually assemble much of a computer with them.
Yes, this relay thing is much too sweet an invention to leave sitting around the telegraphy museum. Let's grab one and stash it inside our jacket and walk quickly past the guards. This relay will come in very handy. But before we can use it, we're going to have to learn to count.
Chapter 7. Our Ten Digits
The idea that language is merely a code seems readily acceptable. Many of us at least attempted to learn a foreign language in high school, so we're willing to acknowledge that the animal we call a cat in English can also be a gato, chat, Katze, KOIIIKa, or Kάττα.
Numbers, however, seem less culturally malleable. Regardless of the language we speak and the way we pronounce the numbers, just about everybody we're likely to come in contact with on this planet writes them the same way:
Isn't mathematics called "the universal language" for