RA-40 DB9 Pinout: 1 - Right (Aux or Tone) Output - Level controlled by R14 2 - Left (Main or Voice) Output - Level controlled by R16 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 large potentiometer R12) 7 - Local Control (Control Revert) Logic Output (Use with JU1 - see note below) 8 - Ground - (Digital and Analog) 9 - External Audio Amplifier Power (6 to 15 VDC) (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-40 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-40 should fail. JU1 controls the polarity of this function, explained below. Jumper JU1 - Control Revert logic polarity. 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. JU1's default is position "B" Jumper JU2 - Audio amplifier and filter powering: Position A = Audio amplifiers powered from USB 5VDC. Suitable for many radio applications where the maximum required P-P voltage doesn't exceed 5 volts. Position B = Amplifiers and Filters powered from external source 6 to 15 VDC. Some radios, like the Yaesu System Fusion, requires more than 5 volts P-P of audio. Many radios have a source of 10 to 15 volts readily available. Must be well filtered but regulation isn't necessary as long as enough current is available for the load. Driving speakers will require a power source capable of several hundred mA., depending on speaker impedance and desired listening level. JU2's default is position "A" JU3 - PTT LED false illumination protection - (added with REV3 and later board revisions): Jumper JU3 is removed to enable this illumination protection. The jumper can be placed if enabling this option creates a problem for a particular installation. Placing JU3 disables the PTT LED false illumination protection. The jumper simply shorts out the diode. Why is JU3 necessary? Partial (or full) illumination of the PTT LED can happen if the radio adapter is connected to a radio that has a PTT switching voltage (bias) of less than 5 volts. This is the case with many portable radios. This situation causes the red PTT LED to partially illuminate. This illumination can also happen with just about any radio when the radio's power is turned off, falsely making it look like the radio is transmitting. JU3's default position is removed.