Murray Combination Switch (Australian) Mk I (Service)

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Description: The switch consists of a striker assembly, and a setting assembly. The striker assembly is a tubular body containing  a spring-loaded striker. One end of the body is threaded to receive a collar, which fastens the cartridge to it, while the other end is pierced by a hole through which the striker head protrudes. A projection on the body is pierced to take an anchor cord, used to facilitate installation. The striker head contains both a slot and an annular groove.

A release plate, release lever, trigger pin, release pin, and safety pin comprise the setting assembly. One face of the  release plate has a keyhole slot which can engage the annular groove of the striker head. A circular hole in another face takes the release pin. An upper and lower hole are provided in two side flanges to take a safety pin. One end of the release lever engages the slot in the striker head, when it is used. A hole in its opposite end is provided for insertion of the release pin, which is simply a stud having a hole in its narrow end. The trigger pin, which is a metal pin with an eye in one end, can be inserted through the hole in the release pin.

The various components of the setting which are used, determine the type of action obtained from the switch.

Use: This device is designed for use in anti-personnel mines and booby traps. It may be used as a pressure, pull, or release-of-pressure switch.

Installing and Functioning:

Pressure-Operation – To install this switch for pressure operation, remove the release pin, trigger pin, and release lever. Unscrew the collar, and remove the cartridge. With the blunt end of a pencil push back the striker until the narrow part of the keyhole slot in the release plate can engage in the groove in the striker. Insert the safety pin in the lo-wer safety-pin hole. Replace the collar and the cartridge case, and fit a detonator or fuse into the end of the cartridge case. Attach the switch to the charge or mine, and withdraw the safety pin.

Pressure on the release plate forces the plate toward the switch body, moving the keyhole slot downward, thus releasing the striker and firing the percussion cap of the cartridge.

Release-of-Pressure Operation – To install this switch for release operation, first set up the device as for pressure operation; column 1. Place the release lever in position over the release plate, and transfer the safety pin from the lower to the upper safety-pin hole. Push the release lever and plate together toward the switch body until the ton-gue on the release lever engages in the slot in the end of the stiker. Install the deveice, with a weight restraining the lever, connect the carge, and remove the safety pin.

When the restraining load is removed from the switch, the release lever is disengaged from the slot in the striker. The freed striker, driven by its spring, then fires the percus-sion cap of the cartridge.

Pull Operation – To install this switch for pull operation, first set up the device as for release operation (above). Insert the release pin through holes in the release lever and plate, and insert the trigger pin. Attach a trip wire to a stake, tree, etc., and then to the trigger pin. Connect the switch to the charge or mine, and withdraw the safety pin.

A pull on the top wire withdraws the trigger pin and allows the release lever to be dis-engaged from the slot in the striker. The freed striker, driven by its spring, then fires the percussion cap of the cartridge.

Disarming: Insert the safety pin in the lower safety-pin hole when the device is set for pressure operation, and in the upper safety-pin hole, when set for release or pull operation. Disconnect the switch and the detonator from the charge or the mine, and then detach the detonator from the switch.

Remarks: Prior to re-use of this switch, examine the cartridge case to see whether an unfired cap is in place.