The headsets used in light aircraft are subjected to some pretty rough treatment, particularly in flying training: repeated connections and disconnections, involuntary pulling of the wires on the connectors, repeated twisting of the microphone, drops and bumps….. the life of an aircraft headset is pretty difficult!
 
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On top of this, the use of the headset gives a degree of comfort and security to the user, so its reliability must be the very best possible. For this reason, it is useful to test the headset from time to time to guarantee that it’s working. I came up with this little circuit to verify that the microphone and earpieces are in good working order. I’ve made two of these: one for the club and one for myself.