Handheld Wireless Microphone Transmitter. Featuring an integrated BETA 58A® microphone cartridge, the BLX2/B58 Handheld Wireless Microphone Transmitter delivers wireless audio with professional clarity and reliability.The BETA58A with BLX2 handheld transmitter is The dynamic vocal microphone precision-engineered for professional sound reinforcement. You will get up to 14 hours of continuous use using 2 x AA batteries (included) and an operating range of 100m. Frequency: 518-542 MHz