The GLXD4 single-channel wireless receiver features revolutionary LINKFREQ Automatic Frequency Management (2.4 GHz frequency band) and battery rechargeability. An integrated battery charge port can charge a spare Shure lithium-ion battery while the system is in use. Allows operation of up to 4 compatible systems in a typical setting, and up to 8 maximum under ideal conditions. Featuring an integrated BETA®87A cartridge, the GLXD2/BETA87A transmits wireless audio with digital clarity and rock-solid reliability. Works with GLX-D® Digital Wireless Systems. Offers up to 16 hours of continuous battery life with Shure lithium-ion rechargeable batteries.