W904-MULTI Features: -Transmitter transmits high quality audio via VHF to W901 series headphones.-Connects to any analog audio source through a 1/8" stereo mini plug.-Headphone get 50 hours of listening time between charges with only an 8 hour charge time.-Superb sound quality without wires or interference.-Powered by classroom friendly internal NiMH battery with 40 hours of operating time between 8-hour charges.-No toxic chemicals, mercury free.-Speaker helps to engage a group of students sitting far away from the audio source without disturbing the whole classroom.-Integrated four channel selector is calibrated to receive VHF frequencies from W900 transmitters and allows to switch between four independent programs without interference.-Speaker operates 4 to 6 hours on a full 8 hour charge.-Speaker with built-in 3.5mm mini headphone jack.-Made in USA. Includes: -Includes (1) W900 multi wireless transmitter, (4) W901 multi channeled wireless headphone and (1) W2020 multi channel wireless speaker. Color/Finish: -Color LED on speaker shows channel selected. Specifications: -W2040 Receivers and W2020 speakers within a 300 foot range.-Switchable between 4 frequencies (Blue - 72.500 MHz, yellow - 72.100 MHz, green - 72.900 MHz and orange - 74.700 MHz). Warranty: -Manufacturer provides 1 year warranty.