Electric Controlled Coupling

In response to command current from AWD control unit, control clutch pull-in force is generated at the electromagnet and torque is generated at the control clutch.
The cam operates in response to control clutch torque and applies pressure to main clutch.
Main clutch transmits torque from input shaft to output shaft, according to the amount of pressure.

Fig 1: Cutaway View Of Electric Controlled Coupling
Courtesy of NISSAN MOTOR CO., U.S.A.
The actual amount of torque transfer is determined by control current as shown in figure.

Fig 2: Torque Transfer & Control Current Graph
Courtesy of NISSAN MOTOR CO., U.S.A.