The Univox 13A Speaker Microphone mounts directly to the speaker to produce clear crisp sound. The microphone cable has a length of 6 ft. and has a 3.5 mm male plug. The input to a loop system is critical to its performance. Electret (condenser) microphones have a high sensitivity and are immune to magnetic fields making them ideal for use with hearing loops. However, they do need phantom power (a bias voltage) to operate.