Sennheiser RS 185 RF Wireless Headphone System Audiophile style open back, circumaural headphone system with excellent digital wireless audio transmission delivering range up to 328ft/100m (line of sight).Connectivity Technology: Wireless High-performance Sennheiser transducers deliver precise, detailed and dynamic sound Multi-purpose transmitter supports both Digital and Analog Inputs in addition Automatic and Manual Level Control - also functions as 'easy-charge' cradle and docking station for the headphones Multi-receiver transmission - transmitter supports up to two pairs of headphones simultaneously (optional HDR 185, sold separately) Two year warranty when purchased from an authorized Sennheiser dealer. Signal-to-noise ratio: [Analog input] ALC typ. 85 dBA at 1 Vrms, MLC  90 dBA, [Digital input] &gt; 90 dBA Frequency response is 17 - 22,000 Hz. Carrier frequencies: 2.4  2.48 GHz Wireless, open, circumaural headphones with uncompressed digital audio transmission Exceptional digital audio clarity and transmission range of up to 328ft/100m (line of sight) High-performance Sennheiser transducers for precise, thrilling sound Control the sensitivity of your analog input  choose between Automatic Level Control (ALC) mode to even out volume differences automatically or Manual Level Control (MLC) mode to manually adjust the sensitivity Supports analog and digital audio inputs and allows toggling between the inputs Balance control located on the headset for convenient adjustments Multi-purpose transmitter  also functions as easy-charge cradle and docking station Multi-receiver transmission  transmitter supports up to two pairs of headphones simultaneously Ergonomic design for enhanced wearing comfort