Also ball-return mechanism . A collection bin mounted below the foot end of a table to which balls potted in any pocket will return by means of gravity assisted gutters or troughs running from each pocket opening to the bin. Ball returns have been in use since at least the 1700s. Pockets which simply collect balls are known as drop pockets . A table without a ball return may be called a "drop pocket table", while a table featuring a ball return may be called a "gully table"., 39 Coin-operated bar tables have ball-return mechanisms that separate the cue ball from the object balls so that the object balls are captured when pocketed until the game ends, then released when paid for again, while the cue ball is continually returned for continued play after scratches. This type of table is dependent upon one of three types of cue ball that can be distinguished from object balls: the Magnetic cue ball , the dense ceramic "rock", and the oversized "grapefruit" ball. Ball return mechanisms have also been devised that use a smaller, lighter cue ball , instead of a magnetic or heavier one.