1. The length of lines in PA system can be about thousands of meters. Signals are transmitted in the mode of high voltage & low current for reducing damping.
2. The PA amplifier's outputs are rated with 70V/100V/150V/200V/250V.
3. The Public address speakers are high impedance with 70V/100V/ 150V /200V/250V input terminals for adapting to the line voltage.
4. The microphone has the priority in sequence of inputs.
5. The lines are used by audio frequency lines.