all pins lead 3.5mm audio connector 5 gold fingers Builtin buzzer (switch switching) With mounting holes Yellow and black differentiated 3PIN interface 5V 1A selfrecovery fuse colour:black Material:ABS size: 56 x 44 x 12mm Package Contents: 1 * Expansion board Note 1. When using power supply, IO port current is less than 200ma, please do not connect high current devices (such as large servo, DC motor), otherwise it burn out . 2. When using a 5V external power supply, you can drive multiple small servos, but please note that the current should not exceed 1A. 3. If you use the high-low read function of the pin, you must set the pull-down on the pin. 4. If P0 is used as a normal IO port, the buzzer toggle switch must be placed on the off side, otherwise the buzzer sound or the IO read value be abnormal. 5. Use the shared pin with the dot matrix (such as 3, 4, 5, 6, 7, 8, 9, 10, 11), remember to disable the dot matrix screen on the software. 6. Do not use IO19,20.19and 20 can not be used as an IO port, only for I2C communication. 7. The USB port allows a maximum input current of 1A. 8. Do not use on metal products to avoid short circuits. Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.