DescriptionSignaling by Napoleonic semaphore line.jpg
English: Illustration of communication by mechanical semaphore in 1800s France. Lines of towers supporting semaphore masts were built within visual distance of each other. The arms of the semaphore were moved to different positions, to spell out text messages. The operators in the next tower would read the message and pass it on. Invented by Claude Chappee in 1792, semaphore was a popular communication technology in the early 19th century until the telegraph replaced it.
This image is from an advertisement by Universal Microphone Co. without a copyright notice published in a 1944 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.