The Electronic Thumb was a short squat black rod, smooth and matte with a couple of flat switches and dials at one end. It allowed hitchhikers to flag down passing spacecraft to hitch a lift. The signal was akin to an emergency signal in that it was omni-directional and limited in range. The success one achieves in attracting a passing spacecraft depends on two things; the proximity, sensitivity and active mode of the spacecraft's receiver and the desire and willingness of the craft's occupants to put up with a hitchhiker for the next leg of their journey.
If one is fortunate, the craft will drop you off at your desired destination, or at least the port of call on their route that you prefer. If one is not fortunate, but still lucky, the occupants may choose to ignore your signal altogether. If one is just not fortunate, you will be picked up only to suffer a fate worse than if you had not signaled at all.
The Electronic Thumb appeared in:
- The original radio / TV drama, where it is called "Electronic Sub-Etha Signaling Device", not to be confused with the Sub-Etha Sens-O-Matic.
- The Douglas Adams book The Hitchhiker's Guide to the Galaxy.
- The Hitchhiker's Guide to the Galaxy computer game.
- The 2005 film
Radio Drama / TV Drama / Novel SeriesEdit
In all three of the original dramatic adaptations, Ford Prefect owns an electronic thumb as part of his role as a researcher for the guide, and uses it to hitchhike across the galaxy. It is a black rod with switches on one end, used to signal passing spaceships.
Arthur Dent finds the electronic thumb in Ford's bag just before they are taken aboard the Vogon spaceships. It has two controls on it, both of which are needed to advance the plot: one which signals passing spaceships, the other which contacts the engineering firm that built the electronic thumb to dispatch a field engineer to help in repair work. In the first case, Arthur (through the player) has only a few turns to figure out to push the first button in order to be saved by the Vogons. In the second case, Arthur can also use to escape from the belly of a sperm whale, when pressing the first button does not help him escape. Pressing the other button summons an engineer robot to repair it.
In the film, the electronic thumb is a metallic ring that is worn on - obviously - the thumb. Holding out one's thumb sends a gleaming beacon light out into the sky, summoning passing spaceships. Ford uses it to help himself and Arthur escape from the Earth just before the Vogons destroy it. Almost as soon as they get aboard the ship, Ford tries sending the signal out through the piping to get off that ship, but cannot get a signal out, giving the Vogon guards time to find them and throw them out into space.