Philips sold a keyboard for CD-i players called CD-i KeyControl. The keyboard could be used to enter Favourite Track Selection names for CD-Audio discs in the player's startup shell, for entering text in CD-i internet applications and for searching in the Dutch encyclopedia and the Dutch medical encyclopedia titles. I know of no other titles that supported the CD-i KeyControl. CD-i developers please note: the CD-i KeyControl is not a terminal-style RS-232 keyboard, it cannot be used for text input in the authoring process or with CD-i development player-based authoring tools like MediaMogul.
Most people will think of the "CD-i KeyControl" (22ER9042) when they hear the term "CD-i keyboard", but there also exists a true "CD-i Keyboard" (22ER9041). The former was introduced in 1996 with the CD-Online discs but the latter is much older, its specification was published in May 1993.
The "CD-i Keyboard" is a full PC-AT style keyboard (without a "Windows" key, and using the term "SuperShift" for what is usually called "Alt") that connects to a CD-i player just like any other peripheral. It was intended for the professional market (specifically, the so-called "CD-IX" configuration) and is colored accordingly (whitish). This is the keyboard that the original CD-i keyboard protocol (later called "K-mode" because of it's ASCII "K" device identifier byte) was written for. It transmits key events in two-byte packets at 1200 baud.
The CD-i KeyControl also supports a so-called "T-mode" which uses a different protocol. The keyboard actually masquerades as a graphical tablet with a device identifier byte of ASCII "T". This protocol transmits key events in four-byte packets at 1200 baud. Why was the "T-mode" introduced when there was already a perfectly usable keyboard device protocol? The reasons for this are arcane, to say the least, and provide a very nice "horror" story about product design and compatibility; it also illustrates the lengths that Philips went to in order to maintain the "All CD-i titles can be used with all CD-i players" principle.
[Thanks, cdifan (cdibits.blogspot.com), Jorg Kennis (www.icdia.co.uk), Retrostuff (www.retrostuff.org), Dee Veedeez]]