In addition to the foregoing mines, specimens of which have been recovered, there are the following types about which there is intelligense information only.

These represent two types of anti-submarine, contact net mines designated by the Japanse as "Type 96" and "Type 96, Modification 1." The maximum depth of water in which the nets are laid is 700", and the depth of the mine case may vary from 8' ro 300'. Drag lines from the head rope of the net to the firing mechanism fire the mines when subjected to suitable tension.

The physical characteristics of the mines are as follows:

Case

Shape – Cylindrical with rounded ends, 20".1 in diameter and 27".2 long.

Material – Steel.

Charge - Apricot – 121 lbs. granular Type 88 explosive.

Grapefruit – 132 lbs. granular Type 88 explosive.

Total Weight – Apricot – 238 lbs.

Grapefruit – 249 lbs.

Firing Mechanism

Modified type 95 depth charge pistol.

Operation

As the net is lowered into the water, a hydrostically-operated detent on the mines restrains the drag lines from transmitting tension to the firing mechanism until a minimum depth of eight feet is reaches. The "GRAPEFRUIT" has the additional safety factor of a shear pin in the firing mechanism to prevent firing on a slight tension. Thereafter, the mi-nes will fire when a minimum tension of 300 lbs. is applied to the firing mechanism through the drag lines.

Safety Precautions

There are no known self-disarming feature.

This is a moored, contact mine laid by surface craft. The Japanese designation for this mine is not known. Unlike the majority of Japanese contact mines, the AVOCADO'S firing mechanism is an impact-inertia pendulum device rather than electrochemical horns.

The characteristics of the mine are as follows:

Case

Shape – Spherical, 32".5 in diameter.

Material – Steel.

Charge – 170 lbs. Type 88 explosive.

Total Weight – 450 lbs.

Operation

Shortly after the mine assembly strikes the water upon leaving, a metal plummet drops away from anchor, reeling out a plummet cable as it sinks. When the plummet rea-ches a depth pre-set on the cable dum is locked and the anchor separates from the mine case and sinks, reeling out mooring cable from a drum. Weight of the plummet holds a spring-loaded pawl from engaging a ratchet on the mooring cable drum. When the plum-met touches the bottom, release of tension on the plummet cord allows the pawl to en-gage the ratchet, locking the drum. The mine is then pulled downward and will moor at a depth below the surface equal to the length of the plummet cord. No further details of the arming procedure are known. When the mine is struck of tilted sufficiently to cause an inertia pendulum to make one of three electrical contacts, the circuit through the battery and detonator is closed and the mine fires.

A moored, contact mine laid by surface craft. The Japanese designation is unknown. The base plate of the "BANANA" is similar to the Dutch Vickers and the British T-MK 3 mines, and may have been copied from them. The general characteristics of the mine are as follows:

Case

Shape – Two hemispheres, 33".5 in diameter, joined by a cylindrical mid-section (width unknown).

Material – Steel.

Charge – 275 lbs. Type 88 explosive.

External Fittings

Horns – Four, electrochemical, equally spaced about the upper hemisphere.

Base Plate – In center of lower hemisphere, containing a straight-shank mooring spindle.

Cover Plate – In center of the upper hemisphere.

Operation

Shortly after the mine assembly strikes the water upon laying, a metal plummet drops away from anchor, reeling out a plummet cable as it sinks. When the plummet reaches a depth pre-set on the cable drum, the drum is locked and the anchor separates from the mine case and sinks, reeling out mooring cable from a drum. Weight of the plummet holds a spring-loaded pawl from engaging a ratchet on the mooring cable drum. When the plummet touches the bottom, release of tension on the plummet cord allows the pawl to engage the ratchet, locking the drum. The mine is then pulled downward and will moor at a depth below the surface equal to the length of the plummet cord. Dissolution of a so-luble washer permits mooring tension to withdraw the mooring spindle in the mine base plate, arming the mine.

The mine fires when one of the horns is bent sufficiently to breask its vial allowing electrolyte to run into a battery cup, generating sufficient current to fire the detonator.

Safety Precautions

A mooring safety switch is designed to open and disarm the mine when tension is re-moved from the mooring spindle. This feature, however, is not dependable.

A moored, contact mine laid by submarines as an offensive weapon and designated by the Japanese as "Type 3, Mark 6". The mine can be planted in water having a maximum depth of 1220'. The case can be moored at a maximum depth of 66'. The minimum depth of the mine case below the surface is not known. The characteristics given below are si-milar to the mine JA, and it is possible that the "PEAR" is an improved design of that mine.

Case

Shape – Two hemispheres, 35".5 in diamater, joined by a 10" cylindrical mid-section.

Color – Green over red.

Material – Steel.

Charge – 440 lbs. Shimose.

Total Weight – 900 lbs.

External Fittings

Horns – Four, electrochemical, on upper hemisphere.

Operation

Nothing is known of the anchor, arming devices or depth-taking mechanism. The mine fires when one of the horns is bent sufficiently to break its glass vial, allowing electrolyte to run into a battery generating sufficient current to fire the detonator.

This mine was reported in CINCPAC-CINCPOA Item #9330 as the Japanese "Type 3, Mark 1 Aerial Mine Model 1, Temporarily Designated 'K'". No other information is known about the "PLUM". The mine JI, recently recovered in the Philippines, is an aircraft laid, drifting mine and is labeled by the Japanese as "Temporiarily Designated K-2". The simi-larity of designation may indicate that the "K-2" is a modification of the "PLUM".

A moored, contact mine laid by surface craft either as an offensive or defensive wea-pon. The Japanese designation is not known. The "POMEGRANATE" is similar to the British Vickers and is equipped with an upper and/or lower copper antenna to increase its ope-ration area. The characteristics of the mine are as follows:

Case

Shape – Spherical, 41" in diameter.

Material – Steel.

External Fittings

Horns – Six, electrochemical, four equally spaced on upper hemisphere, two 180° apart on lower hemisphere.

Antenna – Upper and/or lower, copper cable.

Operation

No information is available on the anchor of depth taking mechanism. The mine fires when the steel hull of a ship contacts the copper antenna, or when one of the horns is bent sufficiently to break its glass vial, allowing electrolyte to run into the battery, gene-rating sufficient current to fire the detonator.

A moored, controlled mine laid by surface craft as a harbor defense weapon and de-signated by the Japanese as "Type 92". This mine used an acoustic monitoring system to indicate the presence of shipping. It is fired electrically from a control post on the beach. The maximum depth of water in which the "QUINCE" is laid is 393', and the normal depth is 98' - 131'. "QUINCE" mines are laid in two rows, with mines spaced 426' apart, and rows 524' apart. The maximum distance of a field of such mines from the control post is 15 miles. The physical characteristics of the mine are as follows:

Case

Shape – Unknown, 48".9 in height.

Charge – 1100 lbs. Type 88 explosive.

Total Weight – 1650 lbs.

Operation

Upon lyaing, the mine assembly sinks to the bottom and the case remains attached to the anchor for approximately one hour. At the end of that time the case rises and assu-mes its correct depth. Reports indicate that these mines are laid in groups of six. Hydro-phones in the mine field transmit sound of approaching ships to the control post, and at the direction of the observer, the mines are fired electrically either singly or in groups.