The device I decided to consider was my portable cd player. Overall, it's a nice player, but it has some features that can be hard to decipher.The front interface is around a circle in the middle. The volume buttons are on the top, one with a plus sign and one with a minus sign and with the abbreviation 'vol' next to it, so one knows exactly what those buttons do. The next and previous buttons are next going clockwise around the outside circle. These are relatively well labeled, but unless you know what the symbols mean, you might not be able to understand what it wants you to do. This also goes for the play/pause button and the stop button, which are the next ones around that outer circle. One good thing about the play/pause button is that there is a raised dot on it, much like the raised bars on the f and j keys on the keyboard, which helps me know which button it is, and be able to find the other major buttons. The rest of the buttons around that inner circle are the ones that can be more confusing. The radio/band and tuning mode buttons are easy to use. They only have one function. Same goes for the equalizer button, but you need to know what eq stands for to understand that. The last three buttons take some getting used to. These have more than one function. I mainly use the farthest one if going clockwise from the top. This is the play mode button. I don't know what exactly the other function does (-city/nor...???), but when playing a cd, this button allows you to change between repeating a single song, repeat the cd, shuffle once through the songs, or shuffle and repeat all the songs. The third of those is not available for use when an mp3 cd is inserted, much to my dismay, but I've gotten used to it.
One feature that is only really explained in the manual is that the radio uses the headphone cord to find the signal. Unfortunately, the headphones I got with the player broke a year after I got it, and it's been a while since then (and I rarely use the radio function on it anyway) so I don't remember whether the quality changed after that.
Overall, I really like my cd player, but for some of the special functions beyond those that are basic, I would definitely need a manual. This is because some of the buttons have more than one function.