Partial fit
3.5 mm TRS plug
A stereo plug in a headset socket. Audio usually works and the microphone never does, which is exactly the kind of failure that looks like a broken device.
- shiftThe plug is one contact short, so its sleeve lands on the jack's ring 2 rather than its sleeve. Ground arrives on the ground contact by luck of the CTIA pinout, but every contact after the ring is displaced by one position.
- openThe jack's sleeve, which is the microphone contact on a CTIA headset socket, is never reached. A headset socket expecting a microphone sees an open circuit and may report no headset at all.