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Summary
DescriptionElectrical bushing assortment 1954.jpg
English: An assortment of electrical bushings made by the American Lava Corp. in a 1954 advertisement in an electronics magazine. A bushing is a hollow insulator that allows a conductor to pass through a metal wall without making contact. These are made of alumina ceramic (porcelain). They have operating voltages that range from a few hundred to about 10 thousand volts (righthand one).
This image is from an advertisement without a copyright notice published in a 1954 US magazine. In the United States, advertisements published in collective works (magazines and newspapers) are not covered by the copyright notice for the entire collective work. (See U.S. Copyright Office Circular 3, "Copyright Notice", page 3, "Contributions to Collective Works".) Since the advertisement was published before 1978 without a copyright notice, it falls into the public domain.
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (50 p.m.a.), Mainland China (50 p.m.a., not Hong Kong or Macao), Germany (70 p.m.a.), Mexico (100 p.m.a.), Switzerland (70 p.m.a.), and other countries with individual treaties.