RR3P and RR3PT are two relay modules serving to control of valve or damper actuators with feedback signal 0 - 10V. The system aims to make a difference between the preset and the feedback voltage was equal to 0V. To meet this condition appropriate contacts of the S1 or the S2 are shorted.

RR3P has electromechanical relays with normally open contacts.

RR3PT has MOSFET solid state relays.