Frequency - US25BD - 537,900 - 540,400 MHz. Handheld wireless system from WMS40 series that is a true plug'n'play wireless solution and provides crystal clear sound. It includes the SR40 Mini DUAL stationary receiver and two HT40 Mini handheld transmitters with a dynamic microphone capsule. The receiver features three status LEDs indicating on/off status, received signal strength (RF OK) and audio clipping (AF CLIP). It provides a volume control and a noiseless on/off switch to protect the connected speakers. It integrates two separate wireless receivers in one compact and lightweight housing, featuring two balanced outputs via 6.3mm jack connector. The supplied switched mode power supply operates on any AC voltage from 110 to 240VAC and includes EU, UK, and US adaptors. Each of the handheld transmitters features a cardioid polar pattern which ensures maximum gain before feedback and the unique HDAP (High Definition Audio Performance) technology that delivers brilliant sound. It also features an on/off/mute switch and a sturdy wire-mesh cap to protect the microphone element. The transmitter's stand-out feature is its extremely long battery life of 30 hours off a single AA battery.