Blake Transmitter

In 1877 Francis Blake invented a carbon microphone for use in the telephone, shortly after Thomas Edison invented a microphone that also used carbon contacts. Blake used a carbon button design that initially would not stay in adjustment, but with later improvements proved to be workable. Alexander Bell hired Blake and put him to work with Emile Berliner who also invented a carbon microphone. The improved Berliner-Blake microphone was standard with the Bell company for many years.