Thank you for the quick response. I have these and I have the modern one, but I am looking for the schematics for the board itself and the microphone. The board appears to no longer be available and the microphone have wires that have come off their internal terminations. I got this as is off eBay and was not working. I do have some experience with printed circuit boards and would like to try and repair it if it is the board and the microphone.