Scratch-built PiIRLP node DB-9-9 wiring #piirlp

Wes AE6ZM
 
Edited

Sorry all. I just discovered the PiIRLP subgroup. Moving this to there. 

I am building up a PiIRLP node from parts I have in my inventory, node is connected to the system and appears to be running OK. Perusal of wiring diagrams seems to show the DB-9 pin 9 is paralleled with the USB sound card Speaker out to feed the radio mic in. This seems different from the PC-based wiring. Am I seeing this correctly? And, why is this pin 9 connection needed?
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VY 73,
Wes
AE6ZM
Node 3343

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