The TrackMan Portable Mouse is a trackball produced by Logitech for use with notebook computers, starting around 1992. Logitech produced both PS/2 and Serial versions of this trackball; mine is the PS/2 version, model number T-CE3.
The TrackMan Portable is designed to attach to the side of a notebook keyboard using a clip. The clip can then be attached to the mouse itself at whatever angle is most comfortable. Additionally, the trackball has a PS/2 cable to connect to the port on a notebook computer, which can be routed to either side of the trackball. It is, however, far too short for most desktop use. Unfortunately, the TrackMan I picked up was missing the clip entirely, so it could not attach to anything. Xah Lee has a page on this trackball with some photos and additional information, including photos of the clip portion.
The trackball has three buttons; the left/primary button is around the outer edge of the curved portion. The right/secondary button is the large bar button at the base of the trackball and the third button is the small dot on the face. The trackball would therefore be gripped as follows, which isn't too far off a typical thumb-operated trackball:
By default, the tracking direction is oriented such that "up" is towards the Logitech logo (e.g. direction my thumb is pointing in the photo above). Unfortunately, the tracking itself is where things start to fall apart. In a word: it's horrible, with very stiff rubber rollers that prevent the ball from coasting at all. If you are used to finger operated trackballs that glide effortlessly, the constant short thumb motions will drive you insane. Obviously there is no expectation that it can compete with a modern optical or laser trackball, but even contemporary steel roller trackballs such as the older models of Kensington Expert Mouse or CH Products Rollermouse will run circles around this.
Opening this trackball takes a bit of effort. There are no screws, so it requires prying the case open with a thin, hard device such as a spudger or jeweller's screwdriver. If you wish to open yours, take a look at the following photos to note the positions of the latches and push against them to disengage.
... without breaking them. Whoops. With it open, let's take a look at what we end up with.
As an opto-mechanical device, there's not really that much surprising here. As expected above, the ball is secured by some basic rubber rollers, similar to a ball mouse. Each of these connect to a slotted, encoding disk which will be read by the decoder itself.
Interestingly, there are four buttons on the PCB, which implies that the left and right hand versions of this trackball are internally identical. Perhaps the button mechanism can be swapped by the user, but I didn't try it. With the problems opening the device in the first place, I'm in no rush to do it now.
All I/O is connected, with a whole pile of surface-mount resistors, to a Motorola chip. It has the following labelling:
330073-00 C1 0, <Logo> D18E LLDR9305
Unfortunately, my web search skills are failing me today; I can't find any data sheets or even a description of what series it comes from. It is most likely a very simple micro-controller or communications chip to encode the button states and optical encoder step counts into the PS/2 mouse protocol.
While an interesting historical curiosity, nobody should use these nowadays. The tracking is awful, it's based on PS/2, it requires a separate clip to attach to anything, and the short cord prohibits desktop use. If you need a PS/2 trackball for retro computing, there are plenty of better options.
For mine, I ended up removing the cable and using it as a desk ornament.