This Handbook is issued as the basic general instructions for the equipment involved. It contains descriptive data and instructions for the operation, inspection, maintenance, overhaul, and testing of the Type CH Computer and associated equipment used with the Central-Station Fire-Control System designed by General Electric Company, Schenectady, N.Y. A Parts Catalog is included as well. The Single-Parallax Computer Model 2CH1C1 and the Double-Parallax Computer Model 2CH1D1 are manufactured by the General Electric Company, Schenectady, N.Y. Single and Double-Parallax computers were used on the B-29 airplane in the Army Air Forces. The single-parallax computers weigh 105 pounds eaach, and one was used with each nose and tale sighting station of the airplane. The double-parallax computers weigh 130 pounds each, and one was used with each ring sight and blister sighting station of the airplanes. Each model number has a letter added on its nameplate to indicate its proper location in the B-29 airplane.