... prompts, easy to operate, can be installed GSM phone cards,two-way intercom function.2.The ... using dual band, tri-band, quad-band frequencies GSM / GPRS industrial module, stable and reliable.11. ... Siren's volume can be adjustable. G3+ GSM ALARM SYSTEM Specifications1. Wireless frequency: 315/433/ ... 1.5-4.7M,EV1527/300K2. GSM frequency: 900/1800/850/1900MHz (quad band)3. Standby Current ...