Operational Characteristisc of AMT 1 (Figure 254). The acoustic component is normally alive, and is actuated first. If now the "M" component is actuated, the ZR II mechanism is energized and runs for 120 seconds. After 1.5 seconds, the vacuum-tube heaters of the "T" component are switches on and given five seconds to heat. After 6.5 seconds, cam switch 6 of ZR II operates, switching out the blocking circuit and switching in the firing circuit of the "T" component. If "T" (subsonic) actuation occurs before 25 seconds after "M" actuation, the mine fires.

If the mine does not fire after 25 seonds, the ZR II switches out the plate supply to the "T": amplifier. At 28 seconds, the "T" amplifier heater current is turned off. This three-second interval is allowed to prevent premature firing due to the cooling of the va-cuum-tube heaters.

At 90 seconds the plate supply is again switched on, ant the "M" component is run through latitude adjustment to assure proper correction in case of faulty adjustment or small changes in the prevaillng magnetic field. This procedure continues until complete, and is switched out at 117 seconds. If this 27-second period is insufficient (as in the case of initial latitude adjustment) the ZR II will go thorugh successive cycles until ad-justment is complete.

At 100 seconds, cam switch 6 does back to its blocking contact.

If the action is triggered by "M" actuation, the "T" component amplifier will not be switched on until acoustic actuation is complete. In the normal case (A-M-T- sequence) the unit will be fired by a subsonic actuation between 6.5 and 25 seconds after magnetic actuation.

Figure 254 – AMT 1 and AMT 2 Characteristics