Question : What is difference between internal and external control signal?
Answer:
1. The internal control signals is connected internal potentiometer with corresponding voltage and current
signals in main board to adjust and control the output
2. The external control signal is supplied by two external 0-5V analog signal corresponding to the main board voltage and current signals to adjust and control the output

Question : How to connection for the remote control terminal/ DB9 Port?
Answer:
1. External (0 ~ 5) V analog voltage regulating signal, which common terminal and the negative output
terminal is in communication with the interior
2. Use should pay attention to "common ground" of interference and potential matching problems,
you should use isolated floating of (0 ~ 5) V analog voltage signal driving source.
3. As picture show