Bell telephone magazine (1922) (14569578077)

Identifier: bellvol25telephonemag00amerrich (find matches)
Title: Bell telephone magazine
Year: 1922 (1920s)
Authors: American Telephone and Telegraph Company American Telephone and Telegraph Company. Information Dept
Subjects: Telephone
Publisher: (New York, American Telephone and Telegraph Co., etc.)
Contributing Library: Prelinger Library
Digitizing Sponsor: Internet Archive



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erubber chemists had wide knowledge.The zinc die casting of the combinedtelephone set was replaced by a plas-tic molding, again based on accumu-lated knowledge. Mica had been se-lected for capacitors on the basis of itsappearance; feeling that much goodmica was being rejected, physicistsworked out electrical tests whichproved so much mica usable that theshortage was alleviated. Early in the war, when coastal citieswere seriously concerned about airraids, the Laboratories was asked todevelop a powerful warning siren.The one It produced had an engine-driven blower, a rotor or chopperdriven by a second engine, and a sex-tuple horn to deliver the interruptedpuff to the air. One was installed onthe highest building In Radio City,New York, and several more in othercities. As A SUPPLEMENT to wire circuits inthe communications zone, the Lab-This replica of a German vacuum tube was oratories developed a micro-wave ra-produced in the Laboratories in three days Jio system operatmg at about 5,000
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1946 Bell Laboratories Role in Victory 121