Telediphone

The Telediphone was an early sound recording system, using cylindrical recording media.

One such system was used from 20 December 1938 at the US Navy radio intercept station at Shanghai, to monitor the Moscow-Tokyo diplomatic circuit, using two recorders. In January 1939 this equipment was reported as more successful than automatic recording equipment trialed for the same purpose. [cite book
last = Skillen
first = Hugh
year = 1989
title = Spies of the Airwaves
isbn = 0 9515190 0 x
pages = pp 500 - 501]

References