A VOICE KEY
Robert S. Owen, CET, Ph.D.
A voice key or voice relay is a device that outputs a pulse when the
subject speaks a sound. This is used to trigger a computer timer
when a person starts to speak, usefeful if we want to measure reaction
time to some stimulus.
The method of the schematic can be used with TTL-level computer data
ports. Another method that can be used on the C-64 computer is to
use a photocell connected to the analog input, optically coupled to a lightbul
driven by an amplifier. Although sluggish in response for absolute
real-time measures, the photocell method was found to be reasonable for
relative real-time measures where differences in reaction times,
rather than absolute reaction times, are of interest. For further
details on the photocell method, see the technical details of the dichotic
studies. The method below is necessary if absolute reaction times
are more important.
C3, R5 = 250 mSec output
MIC = 3-wire electret
must use C6/C7 bypass
C5 = bypass