At 1:10, you can hear the bell.
That’s a Teletype, a remote controlled typewriter from the 1930s. It has an actual bell inside!
Originally, teletypes were used like telephones. Two teletypes were connected together, either by wire, or by radio signals (using an interface that communicated using something like Baudot codes).
Teletypes existed long before the electronic computer, but, in the 1950s, teletypewriters were hooked up to computers, to create interactive computing, where you type something, and the computer responds immediately.
However, to understand the significance, we need to go back years, to IBM and its punch cards.
Before interactive computing, computers were programmed through batch processing. The computer was programmed by typing the program and data onto punched Hollerith cards. (These cards were invented in 1884, to create tabulation machines, to count things.) Then, the batch of cards was headed to the computer operator, to execute your program.
Now with the teletype hooked up to a computer, you could type a command, and the computer would print output. Imagine the power!
Here’s a video of a 1970s minicomputer with a teletype attached. I tried to find one with a 1960s computer, but no luck.
Here’s a 1980s vintage setup with a PDP11 running Unix. This is pretty much the level of technology that created the Internet today. The PDP series was the platform for the most important port of Unix.
At around 9:00 you can see the keyboard, and on the letter “G”, it has a “bell” label.
Imagine two teletypes connected to each other. To make the bell at the other teletype ring, you could press CONTROL-G, the “bell” key. It would send a BEL code. At the other teletype, the bell would ring.
To the left, you see a video screen with a keyboard that resembles a PC. It’s not a PC but a “terminal“, which is also called a “glass teletype”. That’s because it acts like a teletype, but has a glass screen. The terminals made the teletype obsolete.
By the time terminals were being produced, in the 1960s to the 1980s, mechanical parts were being phased out for electronic equivalents. The rough electronic equivalent of a bell is a piezoelectric beeper, a chip that converts an electronic current into a vibration that drives a tiny diaphragm. The terminals had one of these beepers inside it.
Early CP/M and IBM PCs made the terminals obsolete, though not particularly quickly. However, unlike later PCs, early PCs didn’t include sound synthesizer chips. They had speakers that weren’t much better than the beepers.
(The 1977 Apple II had a speaker without an oscillator! Programmers used tricks to get it to produce sounds. 1981’s original IBM PC had the speaker on an oscillator. It was like a super-beeper. This was after video games and home computers like the Atari 400, Commodore Vic, and others included sound synthesizer chips.)
To be relevant, the PC needed to operate in a world dominated by bigger computers that connected to terminals. So, these PCs ran “terminal emulator” software, that acted like a terminal, but was a piece of PC software.
Whenever a CONTROL-G was received, the terminal emulator would run some code that caused the speaker in the PC to beep.
This feature is still supported. Here’s the Linux man page for echo. It can send the “BEL” character, and your terminal emulator might beep! (Or it might not, because the default setting is probably to silence all beeps.)
