Two-way voice intercom counter interphone adopts auto dual-way intercommunication technology, automatic indentification of processing speech signals during a call dose not require any action, ideal for the bank, securities, hospital, bus station etc. Features: Streamlined design, the main unit is made of aluminum alloy, strong and durable. Single cable connection, easy installation. High quality loudspeaker for main unit and extension, high sensitive microphone for two-way intercommunication. Adjustable volume with independent switch. Simple to operate. No need to press any button to achieve auto two-way intercommunication. Double-track adjustment with indicating light with spare audio jack. Specification: Working Voltage: DC12V Plug: US 110-240V Max Working Current: 1000mA Main Sound (sub sound): 2W-2W 100Hz-12KHz Outside Microphone: -42Db Inside Microphone: -42Db Audio Output: Dual-way Main Box Size: 15.8 * 8.7 * 4.6 cm/6.2*3.4*1.8in Deputy Box Size: 7.8 * 2.0cm/3.1*0.8in Package Weight: 678g/23.9oz Package List: 1 * Dual-way Counter Interphone 1 * External Speaker 1 * Power Adapter 1 * User Manual .