ZR II Mechanism. The ZR II mechanism determines the time releations between the influence components of the AMT units. Because of the shorter life of the AT 2 compo-nent, additional switching is necessary to conserve the battery in AMT 1, so a different type of ZR II mechanism is used. Two such mechanisms are known, ZR IIb and ZR IIc and the basic switching in is similar. The ZR II mechaniss are motor-driven cam systems.