RA-33 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)


Local Control is a logic option that can enable a secondary control method.  Some repeaters 
only require one logic lead change to enable internal controls. Not all repeaters have this 
control revert option, but for the ones that do, the RA-33 can feed such a line directly.  
This feature of enabling internal controls will allow the repeater to operate locally if the 
Asterisk application, computer, or RA-33 should fail.  JU1 controls the polarity of this 
function, explained below.

Buffered GPIO logic can be used for several things, including but not limited to, indicating the 
status of the receiver's COS or controlling a CTCSS encoder to gate its output to a transmitter.  
These two functions are outlined in the docunmentation for the RA-42.

Jumper JU1 - Control Revert logic polarity. Default is "B"
Position A = DB9 pin 7 Logic is high when COMM OK LED not lit.
Position A = DB9 pin 7 Logic is low when COMM OK LED lit.
Position B = DB9 pin 7 Logic is low when COMM OK LED not lit.
Position B = DB9 pin 7 Logic is high when COMM OK LED lit.

Jumper JU2 - Optional powering for FL-10 audio filter. Default is "A" 
Position A = Optional filters are powered from USB 5VDC (not recommended).
Position B = Optional filters powered from external source 10 to 25 VDC*.  Must be well 
filtered and probably should be regulated.  

* While the optional audio filters will accept up to 30VDC the voltage of capacitors 
C21 and C23 are rated at 25 volts and that voltage should not be exceeded.

Jumper JU3 - Selects the logic output role on DB9 Pin 7 - defined below. Default is "A" 
Position A = GPIO8 Buffer - active low. Q4 is a buffer for GPIO8 or GPIO4.  
Position B - Q4 is a buffer for the Control Revert function - logic polarity determined by 
JU1