Icom DOES infact provide a diagram of the mic connector. It is marked VERY clearly in the manual that pin 1 is the mic input and pin 7 is the mic ground. Pin 6 is the ptt ground. VERY different from pin 7. Since audio requires a center and a shield,I suggest you us them. Pin 6, ptt ground, is to the case, common ground and audio must float above. gl.es 73. Larry... N2LH .- .-.