Retevis RT-9908 Dual-Way Window Intercom System for Bank Counters Auto dual-way intercommunication without pressing any button Anti-interference and noise-free operation Dual-way audio recording output Compatible with 110 V / 220 V power supply All items are Two-way voice intercom communication technology with automatic speech signal detection during calls Dedicated anti-side tone processing chip with auto-mute function Fully automated call control Integrated microphone and speaker design for easy installation Advanced electro-acoustic circuit design, 3W output power for clear and loud voice reproduction Frequency response: 100 Hz – 15 kHz (main/sub speaker) Internal microphone sensitivity: -38 dB ±2 dB, 20 Hz – 16 kHz External microphone sensitivity: -38 dB ±2 dB, 20 Hz – 20 kHz Dimensions: 158 × 87 × 46 mm Package includes: 1 × Dual-way counter interphone 1 × External speaker 1 × Power adapter 1 × English user manual Applications: banks, securities offices, bus stations