Although you have included the control to check if the vibrator is activated, I have not been able to find any guideline regarding this vibration in the specs :-) I was curious about the 4000 value. Have you seen it somewhere? I would expect the phone to vibrate more or less synchronously when the tones are played so I would expect it to be at least a divisor of 10000 which is the time window when the tones are played and muted. What do you think?