M 101 Circuit - Operation (Figure 157).

Arming. When the mine is dropped, action of the Rheinmetall fuse closes the master switch F. The thermostatic clapper Switch A is normally closed at temperatures above 32° Fahrenheit. If the mine reaches a depth of 24 feet or more, the hydrostatic switch G closes to contact No. 2, and the battery BB energizes fuse delay switch B through fuse W. Upon completion of its delay period, B shorts its heater coil and W blows, as a result of the increased current in the circuit. Battery current is then applied to the magnetic firing circuit.

Switch K is normally closed to contact No. 2 because of the BLUE field of a local mag-net. When current energizes coil S, this magnet is depermed by rapid making and break-ing of contact No. 2 until K no longer tends to close to contact No. 2. Thermistor M then heats until fuse R blows and isolates the A.L.A. circuit. The unit is now alive.

Delay-Action Bomb Firing. If the mine does not reach a depth of 24 feet, G remains on contact No. 1 and BB energizes C. Upon completion of its delay period, C switches over, completing the circuit through the detonator.

Normal Firing. A RED actucation closes K to contact No. 1, completing a circuit through the detonator, hold-on coil L, and thermistor Z. When Z has heated sufficiently, L holds K on contact No. 1 and a current increases to 1/4 ampere fires the detonator.

P.S.E. Firing. The unit is fitted with two photo-electric cells designed to be energized upon exposure to light. The resultant current operates relay H, completing a circuit through H, Z and the detonator. The detonator will fire as above when Z heats suffici-ently.

Figure 157 – M 101 Unit Circuit