Two TRS connectors (also known as jack plugs or phone plugs), a common audio connector. They are cylindrical in shape, with two or more contacts. Originally invented for use in telephone switchboards, jack plugs are still widely used, both in the original ¼-inch (6.3 mm) size and in miniaturized versions. The top plug in this image is for stereo connections, while the bottom is for mono.Image credit: Søren Peo Pedersen
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