Description: The Type 3 Electric Firing Device is the product of Japanese Navy experie-mientation on proximity fuzing of bombs. It is operated on electronic principles, and utili-zes a photoelectric cell and a self-projected beam of light to accomplish proximity deto-nation.

Dimensions:

Length: 16 inches.

Diameter: 11 5/8 inches.

The fuze is enclosed in a black cylindrical sheet steel case which is domed slightly at the forward end. Three transparent glass windows are provided in the domed surface to pro-vide for operation of the projected beam of light, for its reception by the photoelectric cell, and for checking the clockwork safety mechanism. A set of anemometer type arming vanes is mounted on the side of the fuze near its after end. Two three-pronged electri-cal cables are fitted near the base of the fuze, one to connect with the Type 3 electric gaine in the bomb, and the other to connect to an electrical power source in the airplane for purpose of warming up the electronic equipment before dropping. An arming wire is connected to the fuze for the purpose of throwing a gang of arming switches and for freeing the arming vanes upon dropping of the bomb. An access door, three inches square is cut into the side of the casing, and the base of the fuze is recessed and proivi-ded with bolt fittings for fixing the fuze in the bomb.

Operation: The distance above the ground at which the bomb is to explode (between 6 and 15 meters) is set by an indicator near the base of the fuze. Electrical connections to the plane's power source and the electric gaine are made. The arming wire is attached to the bomb rack. The fuze is warmed up from the plane's power source several minutes before the bomb is to be dropped. Upon release from the plane, tension on the arming wire throws switches which change the power source from the plane to the battery in the fuze and start the arming motor in the fuze. The rotation of the motor closes the main safety switch so that power is supplied to the amplifying system. The arming vanes rotate off, and allow another arming switch to close. The fuze is now completely armed, and is projecting a beam of light pulsating at a rate of 900 to 1,000 cycles per second. As the bomb nears the target, this beam of light is reflected back toward the photoelec-tric cell in the fuze. When the refelected light of the proper frequency reaches sufficient intensity, the photoelectric cell current, through the amplifying unit, fires the bomb.

Figure 137 – Type 3 Electric Firing Device.