1、Adopting full-duplex voice intercom communication technology, automatic recognition and processing of voice signals, no operation required during the call. 2、Special sidetone processing chip with automatic squelch function, can effectively improve whistle. 3、Applying automatic call control technology, integrated design between the external microphone and speaker, realize one-line connection with the host. It is easy to install. 4、Comprehensive application of electroacoustic technology experience, selection of electro-acoustic device design with excellent performance, up to 3W output power, clear and loud sound, and high speech resolution. 5、The host is designed with independent internal and external mute switches, can easily control them to meet our needs. Features: Adopting full-duplex voice intercom communication technology, automatic recognition and processing of voice signals, no operation required during the call. Special sidetone processing chip with automatic squelch function, can effectively improve whistle. Applying automatic call control technology, integrated design between the external microphone and speaker, realize one-line connection with the host. It is easy to install. Comprehensive application of electroacoustic technology experience, selection of electro-acoustic device design with excellent performance, up to 3W  output power, clear and loud sound, and high speech resolution. The host is designed with independent internal and external mute switches, can easily control them to meet our needs. Can output two internal and external sound signals (with bank teller recording). With the stereo jack output mode, the recording function is not controlled by the power switch and each function button. Designed with a cable protecting in the main unit, can prevent the connecting plugs from damage. The extension can be hung on a wall or attached to the glass by a strong dispensed tape. Application: banks/securities/hospitals/stations/ the place where install the anti-theft glass. Specifications: Material: Metal + plastic Color: As picture shown Maximum Working Current: 1A Main and Auxiliary Speakers: 3W External Microphone: -38db±3db Internal Microphone: -38db±3db Dimensions:  18.2*13*5.6cm/7.2*5.1*2.2in (Main unit) 6.1*8.5*2.4cm/2.4*3.3*0.9in (Auxiliary unit) Packing Size: 15*12*4cm/5.9*4.7*1.6in Fitment: suitable for banks/securities/hospitals/stations, etc. Especially the place where install the anti-theft glass. Package Includes: 1 * Internal Host 1 * External Speaker 1 * Power Supply 1 * Instruction Manual Note: 1. Please allow 0-1 inch error due to manual measurement, thanks for your understanding. 2. Please note that the new type and old type of this product will be sent randomly, and make sure you will not mind before ordering.