NE555 frequency adjustable; pulse generator module

Specification: 1. onboard 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. onboard power led 5. working voltage: 5~12V 6. Board size: 29 (mm) x12 (mm) NOTE:Can not adjust duty ratio, can only adjust frequency