A microphone blocker is a phone microphone connector used to trick feature phones that have a physical microphone switch to disconnect the microphone. Microphone blockers won't operate on smartphones or laptops because the microphone is controlled with software rather than a physical switch.

A microphone, colloquially called a mic, or mike, is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public events, motion picture production, live and recorded audio engineering, sound recording, two-way radios, megaphones, and radio and television broadcasting. They are also used in computers and other electronic devices, such as mobile phones, for recording sounds, speech recognition, VoIP, and other purposes, such as ultrasonic sensors or knock sensors.