Ультразвуковая ТВ-ремота

[mkll]

21. Zenith Space Command (1956)

The first widely used TV remote control had four buttons (power, volume, channel up, channel down) but no batteries; press a button, and a tiny hammer inside the remote would strike an aluminum rod, transmitting an ultrahigh-frequency tone to control the set. The Space Command ruled the living room for more than 25 years before being replaced by remotes using infrared technology.