RA-25 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 potentiometer)

7 - Not Used - brought to a solder pad to be used optionally.

8 - Ground - (Digital and Analog)

9 - Not Used - brought to a solder pad to be used optionally.