External MIC/PTT/PF interface for Kenwood TS-590SG

      . Circuit design was based on information provided within the following official Kenwood TS-590SG manuals: 1) Instruction Manual, p.3 and p.70. 2) In Depth Manual, p.43. The 4-button membrane keypad is this: http://grobotronics.com/membrane-keypad-1×4.html For my MIC, the approximate values of POTs were set as follows: 5k POT set to ~2.15kOhm (typical, keep this close to 2k) 50k POT (upper) set tp ~3.66kOhm 50k POT (lower towards MIC)…