I am a high school technology teacher in New Jersey. For a communications technology unit I am designing, students will construct telephones from scratch and create a switch board to communicate amongst themselves. My personal background is in ham radio and electronics in the U.S. Navy many years ago. There are many old books designed for young boys in the 30’s and 40’s that show how to construct phones. I have copies in pdf format for anyone interested. Basically you attach a diaphragm to graphite/carbon buttons in a miniature piston cylinder, make a diaphragm, and compress carbon particles to vary the resistance. Sounds simple until you try getting the materials that were available in 1930 now. I thought the acquisition of microphone carbon would be easy: not so. I’ve been experimenting with various forms of carbon granules, ground up pencils, motor brushes, welding rods, carbon zinc batteries, etc. but have not found any granules that function as efficiently as the granules removed from existing telephone transmitters. Anyone out there have any suggestions where to get granules in a modest quantity? Working with high school students, one has to allow for some loss of material and I was hoping for a sack of carbon granules on ebay, to my dismay they are not available anywhere. I’d love to share my research to date with anyone interested. My email is: rconsales@mhrd.org After showing my class the A&E Man, Moment, Machines Video I was intrigued by the resemblance to the unit they held up as an example of the first phone to ones that we are constructing. Would look forward to hearing from anyone regarding constructing early phones.
Regards,
Rich Consales
Morris Hills HIgh School Technology Dept.
Rockaway, New Jersey