An electrical circuit tester includes a first testing device and a second testing device provided in a hand-held housing, each being electrically isolated from the other. The piezoelectric layer is composed of a solid solution containing bismuth sodium titanate and 0. The function deviation indicating frequencies can be comprised in a frequency map. The first task can have an associated first level of interactivity. The method comprises applying an external action to the target device to change power consumption of the target device; monitoring power consumption at each of the plurality of outlets; and correlating the applied external action and the monitored power consumption to obtain the relationship between the target device and the at least one outlet which supplies power to the target device. For example, in accordance with an embodiment of the present invention, techniques are disclosed for providing glitch-free output data from a memory through feedback of the output data signal.