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.