Cebek CD-2 module is a 6-digit standard counter. It counts up from 0 to 999999 when it receives pulses on the signal input. Maximum frequency is 25Hz (Change capacitor C3 to 1µF 63V and the frequency rate can be increased to 100hz) Input signal can be from a volts free source such as a relay contact or switch. The module also has a reset signal input, which allows you to reset the count back to zero.