SIM808 GPRS/GSM+GPS Shield is a GSM and GPS two-in-one function module. It is based on the latest GSM/GPS module SIM808 from SIMCOM, supports GSM/GPRS Quad-Band network and combines GPS technology for satellite navigation.It has high GPS receive sensitivity with 22 tracking and 66 acquisition receiver channels.It has tandard 4-pole TRRS headphone jack so that you can use any 'Android' or 'iPhone'-compatible headset with mic. Also breakouts for external 32Ω speaker and electret mic if you don't want to use a headphone