given the inventive electrical circuit with a device for testing connections in electrical circuits , the change of a test signal due to the effect of a long line is used for determining the quality of an electrical connection . in particular , a determination about the terminating impedance and , thus , about the quality of the connection , is made by defining a maximum value of the test signal reflected at the line end . an existing boundary scan test implementation with appropriate expansions can thereby be used , including a test controller . standard digital signals can be employed as test signal when their propagation time is lengthened by a delay element .