If you just plug timer into your Mac with audio cable (i.e. directly to the Mac internal sound card), it may not recognize timer as sound input device, and don't activate Mic input. Easiest way to workaround this - just buy standard USB dongle sound card, one that has separate Mic input, they are really cheap. And then plug timer into Mic input of USB sound card. And yes, csTimer has stackmat tool within Tools, where you may check stackmat device status, and pick correct sound device where your timer is plugged in.