In the universe of Star Trek, if you are about to beam down to the surface of a planet, and are unaware of what reception you are likely to meet, or indeed what the conditions might be, there are three things you will want to take with you: your communicator, your phaser and your tricorder. It is this third, and possibly most important, item that we shall be looking at in this Entry.

The Tricorder

Technologies have advanced tremendously during the centuries of deep space exploration, but the key elements of the tricorder have remained virtually unchanged during that whole period, and the instrument has been standard issue to all Starfleet officers. So what is so wonderful about this little hand-held, battery-powered device? Well it could easily be a life-saver. Basically the tricorder is able to collect, record and analyse data about its surroundings, for example to determine the age of a rock or the chemical composition of an unknown item, to distinguish human from alien lifeforms, to search for missing people or objects, and to record audio, visual or scientific data about an unfamiliar environment. It can scan through solid materials to a depth of several thousand metres.

The early tricorders, as used by Captain James T Kirk and his crew of the Starship Enterprise in the second half of the 23rd Century, were bulkier objects than those of later generations. Even so, these early ones were only about the size of a thick paperback book¹ and were normally worn outside the uniform, retained by means of a convenient shoulder strap. This left the officer's hands free so they could shake hands (or paw, tentacle, etc) or draw their weapon, depending upon the friendliness of the welcome committee.

The holstered tricorder could be grasped easily and quickly, ready for use. A small screen provided clear display of information and a few simple buttons were used to select the required function of the instrument; it could also be voice-activated. Before landing on special missions, the tricorder's removable data discs could be loaded with special scientific and historical programs downloaded from the Starship's computer data banks. The data captured when visiting a new planet was transmitted to Starfleet's data banks and thus made available to other Starships.

As the tricorder evolved, it provided the same basic functionality, but with greater storage and processing power. The shape evolved also, first to a pistol-like device, then to a palm-sized clamshell-case design, easily carried in a pocket of the officer's uniform, and ideal for single-handed operation. The material from which the case was made was tough enough for use in the field, shrugging off knocks, scrapes and being dropped while protecting the tricorder's technical components. Specialised versions, such as the medical tricorder, were introduced by development of modules to add onto the standard instrument.

A feature of most tricorders is their audio feedback. If searching for something, the device could emit a tone that rose in pitch when it was pointed in the right direction, or a pulse that clicked more rapidly as the distance to the object sought decreased. Later tricorder models were equipped with three touch-keys used to select the type of data input required: GEO (geological), MET (meteorological) and BIO (biological). They also had a prominent red button labelled EMRG – a 'Do Panic' button.

By the 29th Century², the tricorder's capabilities had grown enormously; only the size had shrunk and yet its functions and use would still be recognisable by the officers and crew of NCC-1701.

The Search for Spock

It would be impossible to overestimate the importance of the role of tricorders in the film Star Trek 3: The Search for Spock. They are used first to locate the photon torpedo case that was used as Spock's coffin. It was imperative to find his body due to the volatile nature of the Genesis planet, which was about to be annihilated. The situation was extremely grim, but subsequently the tricorder detected the regenerated child-Spock. His rescuers were able to beam him to the orbiting rescue ship just before the planet exploded.

The Medical Tricorder

The medical tricorder has a detachable, high-resolution, hand-held scanner that sends life-sign information to the tricorder itself. It can check all vital organ functions and detect the presence of dangerous organisms. As well as human physiology, its data banks also contain information on non-human races known to the Federation, thereby making it possible to treat other life-forms.

One of the most memorable uses of the medical tricorder was during the film Star Trek IV: The Voyage Home. The original series crew had gone back in time to San Francisco (Earth) in the year 1986, to commandeer some whales in order to save the Earth of the future. During the mission they 'lost' Lt Chekov, who had injured himself falling while trying to escape arrest aboard the 'nuclear wessel' the SS Enterprise³. Dr Leonard 'Bones' McCoy was searching floors of a hospital for his missing comrade when he happened upon a very sick elderly lady lying on a hospital trolley. He stopped and examined her with his medical tricorder while distracting her from what he was doing by asking what was wrong with her. She said she was awaiting kidney dialysis, which McCoy thought belonged in the dark ages. He reached into his medical bag, produced a pill and gave it to the woman, before continuing his search for Chekov. She swallowed the pill and later on we see her sitting in a wheelchair surrounded by doctors who are acting like wasps round a picnic. The rosy-cheeked, delighted woman excitedly tells passers-by:

A doctor gave me a pill and I grew a new kidney!