SIM808 GSM GPS Modem Serial TTL is a complete Quad-Band GSM/GPRS module which combines GPS technology for satellite navigation. Featuring an industry-standard interface and GPS function, it allows variable assets to be tracked seamlessly at any location and anytime with signal coverage. This Breakout board for sim808 GSM/GPRS/GPS works with external power supply 9 to 12V DC 1.5A current, it can be interfaced with both Serial DB9 and TTL. Initially the ring LED will be on, once the modem is powered on the Ring LED will go off and the Status LED will turn ON, and Network LED Starts Blinking with the frequency of 1sec and once the network is fetched then the frequency of the N/W LED will be 3Sec, this indicates that the device has successfully acquired the network, and at the time of acquiring the network the RF-SYNC LED will glow for the indication of the Network Acquisition.