Abstract: A system can "shadow" the execution of a target-ECS in real time operation, within or without a suite of computers, and record only the necessary information for later re-creation of the real time scenario, without interfacing with the operation of the target-ECS. Such systems include interface means connected by a one-directional bus with the target-ECS and means for converting said input signals to generic input signals, means for converting said generic input signals to unique input events and for providing said unique input events, when needed, to a system connected to said interface means by the bus and including means for storing the unique input events on a permanent storage device during a recording mode and replaying said unique input events during a re-creation mode.