In 1952, GM introduced the Autronic-Eye headlight system that dimmed the high beams when an oncoming vehicle was detected, and then turned them back on when the opposing vehicle passed. The system used a light photosensor mounted in a vacuum tube. The system would then amplify the signal using a tube amplifier so a relay could turn the lights off or on.
In 1960, the system was renamed Guide-Matic. This system used a two-step relay that would allow the low- and high-beam lights to remain on together for one second to tell other vehicles you had a Guide-Matic system. It was called the “Safety Salute.”
GM stopped offering the Guide-Matic system on most of its vehicles by the mid-1960s. But, it survived on some Cadillac models until the 1980s.