Retevis RT-9908 3W/3W Anti interference Noise Free Bank Counter Window Intercom System Dual way Intercommunication Microphone (Silver, 4 Pack) Auto dual-way intercommunication without pressing any button Speaker length 195 cm(75") and enough to install whereever you want Anti-interference and noise-free function;Spare record jack for the bank Appliy to bank securities hospital and bus station Where guard glass again theft is installed Simple and convenient return process;1 year warranty and 30 days no reason to return