Williams AV FM 557 PRO Large-Area Dual FM Plus Assistive Listening Systems with FM T55 Transmitter, (4) PPA R37N Receivers, (4) EAR 022 Earphones, (2) NKL 001 Neckloops
Key FeaturesIncludes: (1) FM T55 Transmitter, (4) PPA R37N Receivers, (4) EAR 022 Surround Earphones, (2) NKL 001 Neckloops, (2) BAT KT6 Two-bay Chargers and Rechargeable Batteries, (1) ANT 005 Remote Coaxial Antenna, (1) IDP 008 ADA Wall Plaque and (1) RPK 005 Rack Panel Kit

SPECIFICATIONS
FM T55 Transmitter:Operating Frequencies: 72.1-75.9MHz , 17 wideband channels (selectable)
Frequency Accuracy: ±2 ppm stability
Deviation: ±75kHz maximum
Pre-Emphasis: 75 microsec
Frequency Response: 31-16000Hz, ±3 dB
Signal-to-Noise Ratio: 67dB Transmited RF
Total Harmonic Distortion: Less than 0.25% @ 1kHz (RF output)
Common Mode Rejection: 57dB @ 1kHz, Mic or Line
Rack Mount: Standard 19" Rack, one EIA rack space high, 1/2 space wide
Ethernet: RJ-45, 10/100 Base-T IEEE 802.3 compliant, unique MAC address
Weight: 3.2 lbs

PPA R37N Receiver:Channels: 17, accessed via seek button in battery compartment
FM Deviation: 75kHz
De-Emphasis: 75µS
Sensitivity: 2µV at 12dB Sinad with squelch defeated
Input Overload: 100mV
Frequency Response: 200–15kHz
Modulation: FM, +/- 75kHz peak deviation
Signal-to-Noise Ratio: 65dB min @ 100uV
Receive Antenna: Integral with earphone/headphone cord
Audio Output: 35 mW, peak into 16 ohms
Weight: 4.6oz

EAR 022 Earphones:Plug: 3.5mm mono
Driver Size: 23mm
Nominal Impedance: 32Ω
Freq. Response: 20-20kHz
Max Power Input: 30mW
Sensitivity: 118dB @ 1kHz
Weight: 15g