There seems to be some confusion on how drive PTT with my Soundcard and DSP driver. So here are some instructions on how to do it
Please note that the Vox circuitry should only be used for 1200 baud AFSK. It is not well suited for 9600 baud FSK
You must adjust the output level of the right channel to the highest possible volume in order to have enough signal voltage to turn on the MOSFET transistor.
Note: Instead of a BC237, most general purpose small signal NPN transistors may be used as well, such as the BC547 or 2N2222.