Headphone jack Private listening with direct monitoring. Compatible with devices that provide a standard headphone output. Power switch and record switch Simple on/off control plus a dedicated recording switch for quick audio capture on compatible devices. Easy to operate without additional equipment. Volume minus / MP3 music conversion key Volume down: allows quick reduction of playback level. MP3 music conversion key: provides access to MP3 conversion functionality where supported by the device. Volume plus / key for song Volume up: enables quick increase in playback level. Song control key: provides a dedicated control for selecting or navigating through songs where supported by the device. Use scenarios On the go: Connect to a handheld audio player or smartphone to privately monitor audio content. Use the record switch to start capturing audio when needed, and adjust volume with the minus or plus keys for comfortable listening. In a portable workspace or DIY setup: Use as a compact control node for portable audio projects. Monitor output via the headphone jack, power the device with the power switch, and manage recording and playback with the dedicated switches and keys. In educational or interview settings: Enable private monitoring during demonstrations or interviews. The volume controls allow quick audio level adjustments, while the MP3 conversion and song control keys simplify format handling and track navigation on compatible devices.