RA-33M DB9 Pinout:

1 - Right (Aux or Tone) Output

2 - Left (Main or Voice) Output

3 - COS Logic Input - (pull near ground required for valid input)

4 - CTCSS Logic Input - (pull near ground required for valid input)

5 - PTT Output

6 - Discriminator / Detector or Receiver Audio Input - (level controlled by the larger potentiometer)

7 - Local Control (Control Revert) or Buffered GPIO Logic Output (Use with JU1 and JU3 - see note below)

8 - Ground - (Digital and Analog)

9 - External Power (10 to 25 VDC*) for optional filters. (Use with JU2 - position B)