XD-53A NE555 Pulse Generator Module Frequency Adjustable for Arduino Specification: 1. NE555 IC 2. Single channel signal output, the output duty cycle about 50% square wave. 3. Plate load resistor, adjust the resistance to control the output frequency. 4. Power LED indication 5. Working voltage: 5~12V 6. Size: 29 (mm) x12 (mm) NOTE: It can not adjust duty ratio, can only adjust frequency. Package Includes: 1PC NE555 Adjustable generator Module