The head unit is in many ways the soul of car audio. Consoles have evolved from simple mono AM radios to sophisticated infotainment systems with lots of quirky signals and one-off projects in between.
Most head units still include an AM tuner, but eight-track cassettes, cassette tapes, and other technologies are history. Other technologies such as the CD may also disappear within the next few years. It may seem far-fetched, but the history of car radios is littered with abandoned technology that was once considered modern.
1930s: First commercial headquarters

Enthusiasts have been finding creative ways to integrate radios into their cars for over a decade, but the first true car radios weren’t introduced until the 1930s. Motorola offered one of the first, which cost about $130 — about $1,800 in today’s money. Keep in mind this was the Model T era and you could buy whole car about two to three times more expensive than the first Motorola car radio.
1950s: AM continues to dominate

Head units dropped in price and improved in quality over the following decades, but they were still only capable of receiving radio transmissions until the 1950s. It made sense because AM stations had a stranglehold on the market at the time.
Blaupunkt sold the first AM/FM head unit in 1952, but it took several decades for FM to really catch on. The first on-demand music system also appeared in the 1950s. At that point we were almost ten years away from eight tracks and records were the dominant force in home audio. Sound recorders aren’t the most reliable medium ever invented, but that hasn’t stopped Chrysler from putting one in their cars. In 1955, Mopar introduced the very first record-breaking headset. This did not last long.
1960s: The car stereo is born

The 1960s saw the introduction of both eight-strip tapes and car stereos. Up to this point, all car radios used a single («mono») audio channel. Some had front and rear speakers that could be adjusted separately, but they still only had one channel.
Early «stereos» placed one channel on the front speakers and the other on the rear speakers, but systems soon followed that used the modern left and right format.
The eight-track format owes a lot to car head units. If it wasn’t for car audio, the whole format would probably be confused. Ford pushed the platform aggressively, and eventually competing OEMs adopted the format as well.
1970s: Compact cassettes arrive on the scene

The days of eight tracks were numbered from the start, and the format was quickly forced out of the market by the compact cassette. The first cassette recorders appeared in the 1970s, outliving their predecessor by many years.
The first cassette head units were relatively hard on the tapes, and Maxell actually based an advertising campaign in the early 1980s on the concept that her tapes were hardy enough to withstand abuse. Anyone who has ever inserted a cassette into a cassette deck at a shooting range will remember the immersive feeling of having the head unit «eat» the precious tape.
1980s: The CD cannot supplant the CD

The first CD head units appeared less than 10 years after the first cassette decks, but the adoption of the technology was much slower. CD players would not become ubiquitous in head units until the late 1990s, and the technology has co-existed with the compact cassette for over two decades.
1990s: CD players become dominant

CD players became increasingly popular in head units during the 1990s, with several notable additions later in the decade. Head units capable of reading CD-RWs and playing MP3 files eventually became available, and DVD functionality has also appeared in some high-end cars and aftermarket head units.
2000s: Bluetooth and infotainment systems

During the first decade of the 21st century, head units gained the ability to communicate with phones and other devices through Bluetooth . This technology was actually developed in 1994, but it was originally intended to replace wired networks. In automotive applications, this technology allowed make hands-free calls and created a situation where the head unit could automatically mute the sound during a telephone conversation.