National Security Agency SIGSALY

Today, digital technology is the backbone of our entire information industry. As a part of this, the transformation of audio information into digital signals is now a routine process which is incorporated into our telephone, television, and music equipment (both recorded and live). Digital communication, measurement and data techniques are quite commonplace. This fairly recent situation was enabled by many things including the invention of the transistor in 1947 and the later evolution of semiconductor microelectronics techniques. However, the pioneering work for many of these capabilities was performed early in World War II in a successful effort to provide secure voice communications for high-level government officials. This brochure presents a brief overview of this revolutionary development.  This is an excellent 19 page non-fiction publication with an amazing amount of fascinating facts and a few photographs.