Cited as a reference
1964 Antique MODEM Live Demo
Why people recommend it
Demonstration of an acoustic coupler modem in operation, linked as a nostalgic example when dial-up and early data links come up.
Watch for: Historical curiosity
In their words
Anyway, you can see one in operation here.
nigel222 on electronics.stackexchange.com, Jul 2019. CC BY-SA.