Chip: SIM800L
Voltage: 3.7-4.2V
Support networks: Global quad-band network
Module size: 2.5cmx2.3cm
TTL serial port for serial port, you can link directly to the microcontroller. No need MAX232
Power module automatically boot, homing network
Onboard signal lights all the way . It flashes slowly when there is a signal, it flashes quickly when there is no signal