A microphone with two separate transducing systems, built into one housing. The two outputs are kept separate, and are fed to two separate tracks on the tape recorder.
"Thank you very much for the prompt service and above all the excellence in which the transfers were made. You accomplished what I thought might be impossible; transferring recordings made back in the 1940's on home made equipment to a CD. We can now hear and enjoy the voices/music that was such a large part of our lives 60+ years ago. ..."