If you are of a certain age, you can close your eyes and hear the sound of a rotary dial phone.
It's one of the common sounds of the beginning of the 20th century that we don't hear anymore.
As a matter of fact, while we can still hear the sound of a phone ringing, we rarely (if ever) hear a busy signal. All calls mainly go directly to voicemail, and it is easy to switch to a different call if one is coming into your cell phone.
Later in the 20th century, it was common to hear the sound of a modem connecting, but this sound is mainly gone. Same with the similar sound of a fax machine answering or connecting.
