Specifications include, but are not limited to: 1. Sennheiser, Model HDE 2020-D-US Stethophone Receiver, or equal (Quantity of Twenty (20) required per each complete system) LC Display indicates channel number, volume level, battery status and RF reception quality Channel selector Volume Control Automatic on/off Integrated rechargeable battery with up to 8 hour of use and quickly charges in less than three (3) hours Modulation: 2 FSK (Frequency Shift Key) Six Channels Frequency Response: 100 – 7,000 Hz Power Supply: Lithium polymer battery Sound Pressure Level: 120 dB SPL at 1kHz Operating Time: 8 hours 2. Sennheiser, Model K 2020-D-US, Bodypack Transmitter; or equal (Quantity of one (1) required for each complete system) Microphone jack socket with individual sensitivity adjustment Microphone MUTE switch Back-lit LCD shows channel selection, battery status, microphone and line levels, and microphone lock mode