Bell Telephone Laboratories - Key to a Crystal Gateway
June 1949 Popular Science

June 1949 Popular Science [Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Popular Science, published 1872-2021. All copyrights hereby acknowledged.

No, this isn't about hallucinogenic bath or ecstasy crystals providing a portal to Nirvana. It is an infomercial promoted by Bell Telephone Laboratories (aka Bell Labs) that appeared in a 1949 issue of Popular Science magazine. Soldering to glass or a rock (quartz crystal) might seem like an impossible task; however, research efforts like this one described by Bell Labs has produced many solder alloys and techniques which have led to robust, reliable, electrically conductive processes used in many applications. Lead has been used with glass for centuries in the form of stained glass windows, but its primary requirement was to ruggedly capture the colored glass shards and to form a watertight seal. Electrical connections, especially at high frequencies, require a more exacting approach. Indium Corporation has long made exotic solder available for unusual applications. I had one of their Research Kits way back in the mid 1980s when working on some classified projects at Westinghouse Electric, which manufactured sonar systems for the U.S. Navy using ceramic crystals for transducers.

Bell Telephone Laboratories Ad

How would you solder a wire to a crystal? This must be done for most of those wafer-thin plates of quartz used in electrical circuits. They play a big part in the myriad-channel telephone system that utilizes coaxial cables.

This is how Bell Laboratories scientists solved the problem: A spot of paste containing silver is deposited on the crystal and bonded to it by oven heat. The crystal is then vapor-plated with a thin layer of silver. Then a fine wire is soldered to the spot by a concentrated blast of hot air. The result is a rugged electrical connection to the surface of the crystal which does not interfere with its vibrations.

Sealed in glass tubes, the crystals are precise and reliable performers in the telephone system. Each is a crystal gate to a voiceway, separating your conversation from the hundreds of others which may be using a pair of coaxial conductors, at the same time.

This spot of paste, this tiny wire, this puff of air are among the tremendous trifles which concern Bell Telephone Laboratories in finding new ways to improve your telephone service.

Above is a coaxial circuit crystal in its glass enclosure. At right the crystal is shown, 3 1/2 times actual size, with connecting wires soldered in position. Weights on wires reflect energy back into crystal, so cut losses.

Bell Telephone Laboratories

Exploring and Inventing, Devising and Perfecting, for Continued Improvements and Economies in Telephone Service