TLK 31 is a “single loop” digital microprocessor-based controller, with ON/OFF, Neutral Zone ON/OFF, PID single action, PID dual action (direct and reverse) control and with AUTO-TUNING FAST function, SELF-TUNING function and automatic calculation of the FUZZY OVERSHOOT CONTROL parameter for PID control. The PID control has a particular algorithm with TWO DEGREES OF FREEDOM that optimises the instrument’s features independently in the event of process disturbance and Set Point variations. Furthermore, the instrument allows for 2 digital inputs and RS485 serial communication using MODBUS-RTU communication protocol and a transmission speed up to 38.400 baud. The process value is visualized on 4 red displays, while the output status is indicated by 4 LED displays. The instrument is equipped with a 3 LED programmable shift indexes . The instrument provides for the storage of 4 Set Points and can have up to 4 outputs: relay type or can drive solid state relays type (SSR)