Peavey ALS 75.9 Mhz Assisted Listening System+4 Receivers+4 Additional Receivers Mhz Assisted Listening System Transmitter And Four Receivers With Ear Buds. Frequency Response 100Hz  15 KHz, +/- 3dB, Signal-to- Noise Ratio 60dB. Total Harmonic, Distortion &lt;0.5%. RF Carrier Frequency between 72-76 MHz. Modulation FM +/- 75KHz max, Operating Range Up to 300 ft. line of sight Frequency Stability +/- 0.005%. Modulation FM +/- 75KHz max, Operating Range Up to 300 ft. line of sight. Transmitter, Mic Input  Connector:  phone jack, Impedance: low impedance, unbalanced, with 9V DC at 1 mA for condenser mic. Line Input  Connector:  phone jack, Impedance: 100 K, unbalanced. Power Output  80,000 uV @ 3 meters. Controls  Power ON/OFF, audio input gain adjust. Indicators  Power ON LED, Audio Modulation LED, Antenna  Permanently mounted telescoping whip. Power Requirement  9V DC, regulated @ 200 mA, AC/DC adapter provided, Dimensions  220 x 121 x 43mm Weight  19.5 oz (600g). Receiver, Controls  Combination VOLUME/ON-OFF wheel. Audio Output  250 mW max into 16 ohms, Connectors  3.5mm mini jack for earphone output, Earphones  Mini binaural ear buds, Antenna  Integral with earphone cord. Indicators  LED power on indicator, Sensitivity  2 uV for 12 dB Sinad with squelch defeated, Squelches at 10 uV for min. 50 dB S-N ratio Mute Threshold  8-10 uV. Power Requirement  (2) AA Batteries, Battery Life  17-20 hours with alkaline battery. Dimensions  110 x 60 x 20 mm, Weight 2.75 oz without batteries (80g). Peavey ALSR 75.9 Mhz Assisted Listening Receiver Body Pack for ALS 75.9 System, Frequency Response 100Hz  15 KHz, +/- 3dB. Signal-to- Noise Ratio 60dB, Total Harmonic Distortion &lt;0.5%. RF Carrier Frequency between 72-76 MHz, Frequency Stability +/- 0.005%