Files W.F.F. Archive Patent and Equipment Records Communications and Cryptographic Equipment Research, 1934-1951
Dr. Edgar Gretener A.G (Teletype and Telecrypto Apparatus)
Dr. Edgar Gretener A.G. Notes
Edgar Gretener Signaling Apparatus Drawings and Article
Hagelin-Gretener System
Letter In Reference to A Cryptographic Device Which Apparently Is Capable of A High Degree of Security
Permutation Switch Px Interchanges Calculations and Diagrams
Swiss-Edgar Gretener Notes
Switch Diagrams
Telecrypto Apparatus Type Tkg 5/14
the Distinct System of Teletypewriters with Pulse Transmission Manufactured by Dr. Edgar Gretenar A.G. of Zurich, Switzerland