212If you are using a baud above 9600 baud and have an older computer, we stronglyrecommend that you consider installing special high-speed, buffered UARTS in theserial port of your computer. These UARTS are available through many parts suppliersand will improve the reliability of high-speed communications. You should ask for the―high-speed buffered UARTS‖ (part number 16550 or equivalent) when ordering fromyour supplier. Newer computers don‘t need this enhancement.Connecting to your RadiosThe 1200-baud radio connector on the KPC-3 Plus rear panel is a 9-pin DB styleconnector, with pin layout as shown below:The purposes of each pin are as follows:1 TXA Transmit audio (AFSK out)2 XCD External carrier detect3 PTT Push-to-Talk4 CTLB (AN0) Control line B (ANØ Analog input)*5 RXA Receive audio (AFSK in)6 GND Ground7 EXT-IN External input for Power/Reset*8 CTLA (AN1) Control line A (AN1 Analog input)*9 GND/RESET Ground (may be configured as external reset)** See the jumper section for details.Pin 1: Connects to the microphone input of your radio, providing the audio signal to betransmitted.Pin 2: When a ground is applied to this pin, the KPC-3 Plus will not transmit packets.This pin is normally used as an external means of supplying carrier detect, but can alsobe used as a ―hardware‖ transmit inhibit.Pin 3: When the KPC-3 Plus needs to key your transmitter, it will apply a ground to thispin. This is an open-drain circuit and requires a positive voltage from your radio (not toexceed 50 V dc or 200 mA).
