Retevis RT-9908 3W/3W Anti-interference Bank Counter Window Intercom System Dual-Way Intercommunication Microphone(Silver,1 Pack) Two-way voice intercom communications technology automatic identification of processing speech signals during a call does not require any action;this model is 110 Voltage Auto dual-way intercommunication without pressing any button;Anti-interference and noise-free function Dual-way audio record output;Dedicated anti-side tone processing chip with auto-mute function Has special side tone processing chip and the movement noise function can effectively improve the noise The voice from this system is clear and natural;this system has top-quality speaker and high-sensitive microphone. Especially the metal tube microphone is deal for the counter and the dual-way intercommunication