Supermarionation (a portmanteau of "super", "marionette" and "animation") is a puppetry technique devised in the 1960s by British production company AP Films. It was used extensively in the company's numerous Gerry and Sylvia Anderson-produced action-adventure series, the most famous of which was Thunderbirds. The term was coined by Gerry Anderson.
The system used marionettes suspended and controlled by thin wires. The fine metal filaments were both suspension-control wires for puppet movement, and electric cables that provided control signals to the electronic components in the marionettes' heads. Although efforts were made to minimise this, the strings controlling the puppets are often visible, although the production teams' ability to mask the strings and the fineness of the strings noticeably improved through the various series.
The heads contained solenoids that created the facial movements for dialogue and other functions. The voice synchronisation was achieved with a specially designed audio filter, actuated by the signal from the pre-recorded tapes of the voice actors. This filter converted the signal into a series of pulses that travelled to the solenoids controlling the puppet's lips. Up to and including Thunderbirds, these control mechanisms were placed inside the puppets' heads. This required that the heads be disproportionately large compared to the bodies. The rest of the body could not be increased to match, lest the puppet be too bulky to operate.
With the advent of miniaturised electronic components in the mid-1960s, a new type of puppet was designed with control mechanisms in the chest, connected to the mouth by narrow rods through the neck. This resulted in a far more proportionate appearance for the puppets, first appearing in Captain Scarlet and the Mysterons. In a 2002 interview, Anderson revealed that it was his desire to move into live-action television during the production of Captain Scarlet and the Mysterons, and that he endorsed the new, realistic design of the Supermarionation puppets as a compromise for his inability to use live actors.