A moored, contact mine laid by surface craft as a defensive weapon against either submarines or surface craft, and designated by the Japanese as "Mark 5, Modification1". The maximum depth in which it can be planted is 689 feet; minimum depth is approxima-tely 55 feet. The maximum depth of the mine case when moored is 164 feet. The JC, found in the Central Pacific, has had limited use.

A description of the case and external fittings follows:

Case

Shape – Spherical, 32".7 in diameter

Color – Black.

Mateial - Steel.

Charge – 182 lbs. block-fitted Shimose.

Total Weight – 456 lbs.

External Fittings

Horns – Four, electrochemical, 90° apart around the upper hemisphere.

Cover Plate – 15" in diameter, in the center of the upper hemisphere, secured by 18 bolts.

Lifting Lugs – Three, equally spaced around the upper hemisphere near the edge of the cover plate.

Base plate – 10".5 diameter in the center of the lower hemisphere.

Support Legs – Four, equally spaced around the lower hemisphere near the base-plate pocket.

Anchor – Not recovered

Mooring Cable – 525' of 0".35 diameter cable.

Operation

Details of neither the anchor nor the depth-taking mechanism are known. Shortly after the mine is launched, however, two switches close to arm it. First, tension on the mooring safety switch; second, dissolution of a soluble plug allows a spring-loaded arming switch in the cover plate to close. The mine is then armed.

The mine fires when one of the horns is bent sufficiently to break its glass vial, allo-wing an electrolyte to run into a battery cup and form a small cell. The resultant current fires the detonator.

Safety Precautions

The mooring safety switch is designed to open and disarm the mine when tension is released from the mooring spindle. The feature, however, is not dependable.

Figure 8 – Cross section of the JC mine.

Figure 9 – Mine type JC