Work frequency: 850Mhz/900Mhz/1800Mhz/1900Mhz (Quad-band) * You can send message command or cancel voice activation function by easy SMS "1111" or "0000" only * Standby time: 2-3 days (If Acoustic Alarm function Off, standby time: 10-12 days) * Compatible with All GSM SIM card * GSM voice/Audio monitor Bug, not suitable for either CDMA or 3G network