MTB40S-UN is a compact plug-on transmitter designed for professional wireless microphones. It integrates Ultrasonic Narrowband protection with a 70 dB filter, supports narrowband and wideband modes, and provides up to 232 MHz switching bandwidth and 2400 selectable channels (40 groups of 60). Powered by two AA cells, it includes 48 V phantom power on the XLR input, IrDA management, OLED display, and ENR/ENC noise-reduction algorithms for clear audio across challenging RF environments. It remains fully compatible with legacy Wisycom receivers.