A series of four separately insulated conductors, generally twisted together in pairs.

A series-parallel combination of transistors; used to obtain increased reliability through double redundancy, because the failure of one transistor will not disable the entire circuit.

One of the small pieces of metal used in typesetting to space or to fill out a line of characters; used mostly to fill space when indenting the first line and to fill out the last line of type.

A unit of heat energy, equal to 10¹⁵ British thermal units, or approximately 1.055 × 10¹⁸ joules.