The Shure BLX24 Vocal Wireless System with SM58 Microphone includes a BLX4 wireless receiver & a BLX2 handheld transmitter with an SM58 microphone. This wireless system is set to Shure's H10 frequency band (542-572 MHz). The system has a 300-Foot range of operation & is designed for an easy setup. The BLX4 receiver's one-touch QuickScan frequency selection locates the clearest available channel & tunes the unit to it. Its LCD display on the front panel indicates the group & channel it is tuned to, which allows you to set the BLX2 transmitter to match. A dual-colored LED indicator appears green for normal audio levels & turns red to alert you if your levels are clipping. The unit has a microprocessor-controlled internal diversity antenna to prevent dropouts & interference. Two AA batteries are included to provide the BLX2 transmitter with up to 14 hours of operation. You can use up to 12 compatible BLX systems at once per frequency band.