Turn ANY radio into an on-demand PA system! Our new PA500 is a self-amplified module designed to be installed in-line between your existing radio and speakers. Simply splice the unit into your existing speaker wires. provide 12 volt power. add any one of our microphones. and it ™s ready to use. System automatically interrupts audio from the radio engages the microphone amplifier whenever the microphone is keyed. All electronics are enclosed in a small module that hides away in the dashboard. 70 watts. Commonly used in primarily public transportation buses and tour coaches.