We control the position of our RL-D joints by using the motor encoder (of our igus stepper motors). In order to define a reference point (or ZERO position), an additional inductive initiator switch (=Ini) can be installed on the joint as an option. The spec. of the Ini switch is given below, it is the same part that igus uses for drylin products. The inductive swich needs a steel part as trigger, we install a set pin in the moving part of our PRT inner ring.
The installation finally looks like this: