Apple has built several prototype televisions that have never been launched, including a see-through set that the company ditched in the mid-2000s. The latest revelations come in a Wall Street Journal article that claims Apple will launch a 4K television next year.

Apple has long been rumoured to be working on a television set, and apparently came close to launching a device just over a year ago, but ultimately decided it wasn't "compelling enough" to launch, according to the WSJ. The dropped 2014 model had a 4K display and was set to include sensor-equipped cameras that would allow people to make FaceTime calls through their television.

However, the most intriguing Apple TV prototype was reportedly built as long as a decade ago. The device had a display that was completely transparent when the television was switched off, and used lasers to beam the image on to the glass when it was turned on. However, the device never got further than the Apple labs because it required "an enormous amount of power" and the "image quality was poor", the WSJ reports.

Apple TV 2016

Despite the aborted launches, Apple hasn't given up on the idea of making a television. On the contrary, Apple investor Carl Icahn says he now expects the company to launch a 4K television set next year in an open letter sent to the company's CEO Tim Cook. Although it should be noted that Icahn tacitly admits he's outside of the loop on Apple's future product plans.

"While we respect and admire Apple’s predilection for secrecy, the company’s aggressive increases in R&D spending (and some of the more well-supported rumours) have bolstered our confidence that Apple will enter two new product categories: television and cars," Icahn writes. "Combined, these two new markets represent $2.2 trillion, three times the size of Apple’s existing markets (if we exclude Apple Watch)."

Icahn predicts Apple will continue to produce the existing Apple TV set-top box alongside its new set. "In addition to an Ultra High Definition television set, we expect Apple to launch a related suite of tiered products and services, including a 'skinny bundle' of pay-TV channels (partnered with various media companies) and an updated Apple TV micro-console (which will continue to service the massive install base of televisions offered by other OEMs)."

Icahn says other Apple products will also hook into the television. "We believe this move into TV will also benefit all the other devices and services in the Apple ecosystem," Icahn writes. "As just one of many possible examples of this, the Apple Watch could perhaps be used as a remote control. Similarly, as we expect Apple to launch a larger 12.9in iPad, it would offer an enhanced viewing experience for an Apple pay TV service, or act an improved 'second screen' to an Apple Ultra HD television."

Whilst Icahn almost certainly has no first-hand knowledge of Apple's forthcoming products - not least because his predilection for drawing attention to himself contrasts sharply with Apple's infamous desire for secrecy - Tim Cook has dropped hints this year that Apple is planning something big in the television market. We may even find out more about the company's plans at next month's WWDC conference.

Icahn says he doesn't expect an Apple car to arrive until 2020.