The original 1⁄4-inch (6.35 mm) version descends from as early as 1877 in Boston when the first telephone switchboard was installed[10] or 1878, when an early switchboard was used for the first commercial manual telephone exchange[11][12] in New Haven created by George W. Coy.[13][14]
The original 1⁄4-inch (6.35 mm) version descends from as early as 1877 in Boston when the first telephone switchboard was installed[10] or 1878, when an early switchboard was used for the first commercial manual telephone exchange[11][12] in New Haven created by George W. Coy.[13][14]
https://en.wikipedia.org/wiki/Phone_connector_(audio)
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