Telex ST-300 SoundMate Wireless Personal Listening System Transmitter On the back of the unit is a balanced XLR-3F as well as an unbalanced 1/4 input. Front panel controls and LCD display allow the user to select mic, line, and 70 volt input options, attenuate the input levels and change hi/low RF transmit power. A new feature called Enhanced Dynamic Range (E.D.R.) works with the SR-400 receiver to provide clearer, more dynamic audio.