module description
1 module S8550 driver transistor 
2 Operating voltage 3.3V-5V 
3 a fixed bolt hole for easy installation 
4 small PCB board size: 3.2cm * 1.3cm 
5 When the I / O port input low, buzzer vocalization

Second module interface specification (3-wire)
1 VCC 3.3V-5V external voltage (can be connected directly to the 5v and 3.3v MCU MCU) 
2 GND External GND 
3 I / O external microcontroller IO port