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If you are using a baud above 9600 baud and have an older computer, we strongly
recommend that you consider installing special high-speed, buffered UARTS in the
serial port of your computer. These UARTS are available through many parts suppliers
and will improve the reliability of high-speed communications. You should ask for the
―high-speed buffered UARTS‖ (part number 16550 or equivalent) when ordering from
your supplier. Newer computers don‘t need this enhancement.
Connecting to your Radios
The 1200-baud radio connector on the KPC-3 Plus rear panel is a 9-pin DB style
connector, with pin layout as shown below:
The purposes of each pin are as follows:
1 TXA Transmit audio (AFSK out)
2 XCD External carrier detect
3 PTT Push-to-Talk
4 CTLB (AN0) Control line B (ANØ Analog input)*
5 RXA Receive audio (AFSK in)
6 GND Ground
7 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 be
transmitted.
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 also
be used as a ―hardware‖ transmit inhibit.
Pin 3: When the KPC-3 Plus needs to key your transmitter, it will apply a ground to this
pin. This is an open-drain circuit and requires a positive voltage from your radio (not to
exceed 50 V dc or 200 mA).
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