Philips and MicroTouch Systems jointly developed a controller to make this touchscreen-monitor work on CD-i and it plugs directly into the CD-i's controller port

 

CD-i member Patrick Selten found this article in Infoworld magazine dated August 8, 1994, which you can find here. It shows a CRT Touch Screen by MicroTouch Systems and ELO Touch Systems, compatible with Mac and CD-i. It is branded the Truepoint, which is combining the Philips PA3520C professional monitor receiver with the Microtouch analogue touch screen. The article gives away a few details how the touch screen actually works, something we've been wondering about in the past when we discovered the Videotronic Touchscreen CD-i unit for example. MicroTouch and Philips jointly developed a new controller to make it compatible. It sais the screen plugs directly into the CD-i player's input port.