... .9. Intercom function: can communicate with the scene people ,two-way intercom.10. Listen-in function: can hear the voice of ... , AC and DC automatic shift, automatically recharge.16. Wireless alarm system, no need to set wire and easy to install.Technical ... lamp,billboard,farm,orchard,fishpond, parking lot. Business/Home GSM alarm system is widely used in the security devices, data surveillance and ...