Designed by David R. Dietrick (who produced the visuals and the original concept) and William John Wheeler (who wrote the actual game mechanics behind it), the Display was a two-sided cardboard sleeve with an illustration of a tricorder on one side and a computer panel on the other. Each side had a series of small windows cut out of the sleeve. These windows were associated with cardboard wheels that were attached to the sleeve with brass fasteners. By spinning the wheel, a different entry would appear in the window, such as "Bird/Avian" or "300" or "Romulan." There was also a larger window at the top through which cardboard strips with pictures (inserted into one side of the sleeve) could be viewed.
The idea behind the tricorder was that the Display could be used to simulate a character's use of a tricorder or a sensor panel aboard a starship. Whenever a skill roll was attempted in the game, depending on the result (and the overall rating of the character attempting it), the referee would consult a 16-page booklet included with this product. There, he'd find charts listing "data" that he could then impart to the player by stating, for example, "Turn Wheel A to 23," which would result in the player learning that the object being tracked was "moving laterally." As there were four wheels, plus the larger window display, more data could be imparted for more successful skill rolls, thereby simulating what a character might learn from a particular adept use of technology.
The Display is not without flaws, the most significant being that the information listed under each data wheel didn't always follow a logical sequence or progression, meaning that, until the referee gained some facility with the information, he might have to spend some time looking on several lists to find just which wheel contains "silicon based" or "a billion." Likewise, there were limits to how much detail the Display could impart with just four wheels and one window. Extremely specific information, never mind concepts unique to a referee's adventure or without precedent in previous Star Trek episodes/movies, had to be imparted "the old fashioned way" rather than by recourse to the Display.
Despite that, I really liked the Display. It certainly made playing the science officer more fun. In the past, it was fairly typical to see something like the following:
Captain: Science officer, what do your sensors show?In short, the science officer was reduced to being a parrot or, worse yet, cut out of the dialog entirely as the referee simply imparted information that, in the game, only someone using the right device could know. With the Display, the referee could pass along information to the science officer "secretly," thereby giving him the chance to reveal what he has discovered. It's a small thing perhaps, but I generally found it added fun to the game, even if it had its drawbacks and limitations. I'm not usually one to recommend the use of props in a tabletop roleplaying game beyond really basic things like mock newspaper articles and similar documents, but the Star Trek Tricorder/Starship Sensors Interactive Display is a rare exception I happily make.
Science Officer: (rolling) [To referee:] I got a 35; what do they show?
Referee: There's a starship of unknown design fleeing the system at Warp 3.
Science Officer: [To captain:] There's a starship of unknown design fleeing the system at Warp 3.