The BLX series bodypack transmitter works with lavalier and headset microphones. With the WA302 1/4" to TA4F cable, it also works for electric guitar or bass. The beltpack features an On/Off hard toggle switch, preferring to eliminate the multi-function push button that is used on some wireless transmitters. Many users found the multi-function single button to be inconvenient and unreliable. This system comes with the BLX bodypack, the WA302 cable, and the BLX4R rackmount receiver. The BLX4R is a rackmountable version of the BLX4. It is is a half-rack sized wireless receiver built into a rugged metal chassis. It features advanced capabilities usually unavailable in wireless systems in this price range. Rack hardware is included. Consumer Alert: Most users do not need a license to operate this wireless microphone system. Nevertheless, operating this microphone system without a license is subject to certain restrictions: the system may not cause harmful interference; it must operate at a low power level (not in excess of 50 milliwatts); and it has no protection from interference received from any other device. Purchasers should also be aware that the FCC is currently evaluating use of wireless microphone systems, and these rules are subject to change.  FEATURES Up to 12 compatible systems per frequency band (region dependent) Microprocessor-controlled internal antenna diversity One-touch QuickScan frequency selection quickly locates the best frequency 1/4" and XLR audio outputs Warranty 2 years.