Main features: Provide accurate reverse polarity billing signal Display Caller ID Add prefixal code automatically: The telephone setting can be set up to add the local area code when dialing local fixed calls and add IP prefixal code when dialing long-distance calls. Locking wireless terminal, locking SIM card, locking service provider and locking districts ( Optional) Parameter management: Parameters can be modified by hand via the connected telephone. Set up or cancel call diverting Support PBX Adjusting the volume of voice: microphone volume and speaker volume can be adjusted separately. 4-in-1 antenna combiner is used: SCG-8QE use 2 antenna; SCG-4QE use 1 antenna. Technical Specifications Environmental Temperature: -10¡æ to +40¡æ .Relative Humidity: 10% to 95% Air Pressure: 86Kpa to 106Kpa Environmental Noise: ¡Ü60dB(A) Working Frequency: Automatically switch among GSM850Mhz /900 MHz/ 1800MHz/1900Mhz Frequency Stability: Better than 2.5 PPM Signal Sensitivity: -103dBM Transmit Power: £¼2W Power supply: AC 220V?5V.