Rotary telephone dial
c. 1919–1985
Band-passed noise, a damped 170 Hz thump, a governor's whirr
You dragged a hole round to the finger stop and let go. A spring and a centrifugal governor walked the dial home at a fixed speed, breaking the line once per unit: seven times for seven, ten for zero. The exchange counted the breaks. Replaced by push-buttons, which were replaced by a picture of push-buttons.
Drag a digit to the stop, or just click it. The clicks are counted honestly.
Dial-up modem handshake
1991–2006
Paired sine waves, frequency-shift keying, band-limited noise
Two machines introducing themselves down a line built for voices. The speaker was left on so you could hear if a person answered instead. Success was announced by sudden silence: the modems carried on at full volume and simply stopped letting you listen. Replaced by broadband, which connects without ceremony or apology.
- 0.0 sDial tone. The exchange says it is ready.
- 1.5 sSeven digits, each a chord of two sines.
- 3.4 sAnswer tone, 2100 Hz. Its phase flips to tell echo suppressors to stand down.
- 5.2 sWarble. Each side lists what it can do, slowly.
- 6.7 sProbing. Tones and chirps to measure the line.
- 7.9 sTraining, then scrambled data. Then, for you, nothing.
Typewriter bell and carriage
1874–1990s
Struck noise bursts, a bell of three inharmonic sines, a ratchet
The bell meant about eight characters remained: finish the word or reach for a hyphen. Then the left hand swept the lever and the whole carriage flew home with a zip and a thud. Survives as the word “return” on a key that returns nothing, and as two invisible characters at the end of every line.
Type on the keys. The bell rings at the eleventh character.
Television switching on
1950s–2008
A 15,625 Hz sine (kept quiet), decaying mains hum, high-passed noise
A thunk as the degaussing coil shook stray magnetism out of the tube, a rustle of static across the glass, and a whine at the line frequency which children could hear from the street and their parents could not hear at all. Switched off, the picture fell into a bright dot that took its time. Replaced by flat panels, which are silent and never quite off.
Flip the power switch. If you cannot hear the whine, the spectrogram can.
Film camera, motor wind
c. 1975–2004
Three noise transients, a geared sawtooth
The clack is a mirror getting out of the way; the click inside it is the shutter; the whirr is a motor dragging the next of thirty-six frames into place. Each press cost money, which concentrated the mind. Telephones still play a recording of it, so that everyone nearby knows a picture has been taken.
Press the shutter release. The roll ends at 36, as rolls did.
Floppy disk drive seek
c. 1976–2011
Pulse trains, one click per track, resonant noise
A stepper motor moves the read head one track per pulse: eighty tracks, eighty clicks, the grunt of a computer thinking where you could hear it. Step the head fast enough and the clicks blur into a pitch, which is how hobbyists taught drives to play scales and, eventually, anthems. Replaced by the flash drive, then by nothing you can hold.
Compact cassette
1963–2000s
A computed tune on a variable-speed loop, hiss, two clunks
The play key was a lever, and you felt the head rise to meet the tape. Then hiss, and half a second in which the music climbed up to speed, slightly seasick. Hold fast-forward and the song went by as a squeal you could navigate by. Replaced by the skip button, which finds the next track but never the middle of one.
Press the keys: play, fast-forward, stop.
Slide projector advancing
1961–2004
100 Hz hum, filtered noise, a solenoid thump and a falling slide
Under the fan's steady hum: clunk, the old slide is lifted out; chunk, gravity delivers the next. Between them the room went dark for exactly as long as it took someone to say “next slide, please”. One in every tray was upside down. Replaced by the slide deck, which kept the vocabulary and lost the fan.
Click the projector for the next slide. There are four. One has a thumb in it.
The time, by telephone
1936–, unrequested
Six sine pips at 1 kHz, five short and one long
You dialled a number and a recorded woman told you the time, precisely, for as long as you cared to listen. We cannot synthesise her, so the collection holds the pips instead. The long one begins exactly on the next ten seconds of your own clock; the exhibit will wait for it. Replaced by every other object you own.
Your clock reads --:--:--