#Trivia: This was the world's first remote control (sold), the [Zenith Space Command], from 1956.
There were no electronics in the remote itself, but rather the buttons triggered a mechanism that struck an aluminum rod that produced an ultrasonic tone which an acoustic reciever in the TV itself picked up.
Ultrasonic remotes were the norm through the 1980s, although the mechanical remotes were soon replaced with electronic ones.

I still remember picking up a remote in the early 1980s and hearing the ultrasonic tones it produced.