This is directed to systems and methods for detecting the insertion of a plug in a device port without physically contacting the plug. For example, systems and methods are provided for detecting the insertion of an audio plug into an audio jack without using physical contacts placed in the periphery of the audio jack. In some embodiments, an electrically conductive element (e.g., a circuit board trace) can be provided on a surface of the port or within the port wall. When a metallic or conductive plug is inserted into the port, the plug can interact with the conductive element and cause a change in capacitance or induction detected by appropriate circuitry coupled to the conductive element. In some embodiments, an optical sensor can be used to detect a plug placed in a port. In some embodiments, the electronic device can detect distinguishable attributes associated with the contact between the electrical contact of plug and port contacts using an appropriate sensor (e.g., a microphone or an accelerometer).