You also need two NPN transistors for COM TXD/FSK and RTS/PTT, 4 x 3K3 resistors, 2 x 10 nF RF blocking capacitors and stereo cable from AF OUT to line in! You can always make it more complicated with USB interfaces :-) I do FSK via LPT port STROBE with MMANA EXTFSK on single COM port on IBM T30 notebook. UE DE MARIO, S56A, N1YU