Self-contained Crakker finds source of intermittent I/O problems and first-outs in PLC or relay logic systems. Logic/timing analyzer monitors up to 16 I/O channels, with inputs ranging from 5 Vdc to 400 Vdc/280 Vac. Voltage transitions as fast as 165 µsec can be recorded and captured for review and manipulation on company's Windows-based software. Two programmable alarms stop process or warn operator when fault occurs.