I am looking into connecting a TNC-Pi to a Kenwood TM-241A for AMPRNet operation. I thought it was going to be fairly straightforward as each pin on the TNC-Pi seemed to have its own analogue on the transceiver's end, until I came across this diagram:
I have a few questions about this. For one, why does it use the external speaker output instead of the Rx output pin on the transceiver? Second, why does the TNC connect to the transceiver's ground instead of the microphone input ground? Third, what are those little circles that seem to loop around another wire?
I did notice that this diagram isn't specific to the TNC-Pi, so I might not have to worry about any of this.