=  NOW 15 WPM  =  TEXT IS FROM APRIL 2023 QST  PAGE 57  =

ARE STILL FOUND IN MANY HAM SHACKS, BUT MOSTLY AS PART OF AN ANTIQUE
COLLECTION.  THESE MICROPHONES CREATED AN ELECTRICAL OUTPUT CAUSED WHEN THE
DIAPHRAGM FLEXED THE CRYSTALLINE SUBSTRATE, WHICH EXHIBITED AN ELECTRICAL
VOLTAGE THAT REPLICATED THE SOUND WAVE THAT EXCITED IT.  THESE MICROPHONES
HAVE A VERY HIGH OUTPUT LEVEL, AS WELL AS HIGH IMPEDANCES AND AN
ACCENTUATED FREQUENCY RESPONSE FROM 2 KHZ UP TO WELL ABOVE THE HAM
BANDWIDTH.  IN ORDER TO WORK WITH MODERN HAM TRANSCEIVERS, THEY USUALLY
=  END OF 15 WPM TEXT  >