5V Ultrasonic Distance Measurement Control Board Rangefinder + HC-SR04 Sensor. 8 bit MCU module. Three 10mm red 7-segment display. Supports serial port display and digital tube display. Valid measurement distance: 3-400cm. TX: module serial port transmit pin. RX: module serial port receive pin. NRST, SWIN: preset STM8 program download port. VCC,GND: 5V power interface, 2-pin 2.54mm socket (fits our connector SBC-2). Six pin serial port. Board size 24.5mm x 35.1mm