Hello @Nadowa
You will need to contact Cedrus for this information. Notice that SV-1 Voice Key is no longer available.
I have used this VoiceKey with some other software and found it rather unreliable. In the end, we recorded the VoiceKey trigger on one channel of an audio recording and the participant’s response on the other channel. We then manually measured the delay between the VoiceKey trigger and the speech onset.
I suspect that the poor quality was due to the poor quality of the microphone supplied with the Voice Key. Using a better microphone might improve the quality of the measurement. Cedrus now offers an RT device called Riponda, which has voice key support (3.5 mm jack). It allows you to connect any microphone. An alternative to Cedrus is Black Box (I have never used Black Box).
Have a look here and here to get a better understanding of the problem.
Best wishes Jens