This is a square wave pulse generator module based on the ubiquitous NE555 timer IC. The module can be powered from a wide power supply range (5 to 12V) and will produce a continuous square wave output between 4Hz to 1.3KHz which can be set by on on-board multi-turn potentiometer. Module has ten-turn frequency adjustment control and power on LED. Useful for applications where an approximate frequency clock source is required such as for stepper motor step generation etc

Reed switch is a kind of passive electronic switching component with contacts with a simple structure, small size and easy to control. It consists of a sealed glass envelope where there are two ferrous elastic reeds and is filled with inert gas called rhodium