This active module 2 oscillators 1 monoflop and a small basic program allow you to check the function of all ports of your c control i m unit 20 and 12 with adapter including irq da1 da2 f1 f2 when you are not sure whether there is a fault or defect in your hardware or there is a programming error this module provides good service and saves you lots of time in trouble shooting suitable for a e 20 12