The latest episode of "Adventures in Tech" explores the surprising origins of Sony's Walkman, and how this legendary device was actually a slightly-tweaked version of an existing Sony product.

To celebrate, CNET has tracked down three rare and iconic Sony devices -- the original TPS-L2 Walkman, the sequel WM2 and the Sony Pressman, who's importance will become clear very shortly. Click through for a lesson in tech history, or hit the link below for the full-fat video version.

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First up, meet the Sony TCM-100 voice recorder, also known as the Pressman. Ours is labelled the TCM-600, but don't worry -- that's just a name it was given in different markets. This humble gadget would form the basis of Sony's iconic Walkman device.

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The Pressman was a tape recorder, aimed at reporters who needed to record audio onto a cassette tape.

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...Of course, once audio was recorded, you could also listen to that sound back.

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The Pressman was a full recorder packed with features, including sockets for an external microphone and headphones. Pay particular attention to the layout of these buttons, because they'll be important later.

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On the side were playback controls, and a microphone.

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In his book Made in Japan, Sony's then-chairman Akio Morita describes seeing his colleague using a Sony voice recorder to listen to music, using a pair of chunky headphones.

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It dawned on them that by removing the key feature of their product, they could create something much more exciting -- something designed purely for listening to music.

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The Pressman was chosen to form the basis of the new product, having proved itself reasonably durable, with plenty of spare parts already out there in case anything went wrong.

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Sony's engineers stripped the Pressman down, ditching the recording circuit and speaker, and replacing them with a stereo amplifier.

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An extra headphone port was added so two people could listen at once, and the Pressman's "Record" button became the Hotline, a button-activated microphone for speaking to your listening partner.

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At last, the TPS-L2 was finished. Gaze upon it folks, this is the very first Walkman. Remarkably similar to the Pressman, non?

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Dual-volume controls let you alter the volume of either the left or right channel.

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Other playback controls remained remarkably similar. Even the microphone remained -- now used by...

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...the famous "Hot line" button! This feature was scrapped after the first Walkman, as Sony found people tended to use the new product by themselves.

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The TPS-L2's fast-forward and rewind buttons.

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Our TPS-L2 is an early model, because it doesn't have the Walkman branding on the side. It was originally called the Soundabout in the US, and in the UK it was the Stowaway, which makes it sound like it's going to hide in a grog barrel and eat all your ship's biscuits. Sony eventually settled on Walkman for every region, however.

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The TPS-L2 came with a soft leather case, that easily outclasses most bundled cases you get with gadgets nowadays.

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The back of the case added a belt clip, so you could strap the TPS-L2 to your clothing.

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The TPS-L2 was a hit. Sony sold its entire stock of 30,000 units in 2 months.

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Sony boosted its popularity with smart marketing, including hiring young couples to walk around Tokyo listening to the Walkman, and presumably looking trendy.

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In 1981, Sony revealed its second Walkman, the WM2.

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The WM2 was much smaller, thanks to some reorganised components, and control buttons positioned on the front of the device.

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The belt clip attachment hooked onto the WM2 via this metal handle.

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This time, there were no arguments over the Walkman name.

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That black stripe across the WM2 is a chunky removable belt clip.

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Here's the WM2 without its belt clip. Looks a bit naked to us.

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The dual-volume controls from the first Walkman were ditched in favour of this handy wheel, and the "Hot line" button was scrapped.

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The dual-headphone sockets remained, however. Can we get these on modern smart phones, please?

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Although the WM2 was scarcely bigger than a cassette tape, Sony found ways to make subsequent models even smaller.

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Does this bring back memories of long car journeys, and finding a pencil to wind your tapes with?

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Unfortunately there's one thing we weren't able to show here -- the original, miniature headphones that came bundled with the Walkman. Sony's Akio Morita says that developing these tiny 'phones was one of the most difficult parts of the Walkman project.

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Sony created a groundbreaking new type of gadget by simply removing a feature from an existing device. Yes, folks, sometimes it really is that simple.

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Despite an onslaught of rival devices, Sony remained the king of portable tunes. Ten years later Walkman sales hit 50 million; in 1992 they hit 100 million, with dozens and dozens of different models available, from toughened waterproof models and solar-powered players.

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The Walkman spawned the Discman, then MiniDiscs and MP3s, before Sony's reign over portable music was finally ended by Apple's iPod. Its eventual demise doesn't lessen its enormous impact, however.

Sony's Akio Morita later said he didn't believe any amount of market research could have predicted the Walkman's success. Instead, it will stand as one of technology's great lightbulb moments.

Salute your Walkman memories by watching our full video, which is packed with much more information on the origins of this incredible machine.

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