Abstract: A method and apparatus for observing an internal state of an electronic component in an electronic system comprising one or more electronic components. The apparatus consists of an electronic switch, a second electronic component, and a control circuit. The electronic switch can be operated in a first mode or a second mode. A first set of terminals on the electronic switch is connectable, in the first mode, to the first component to intercept both the signals being transmitted to the first component by the electronic system and the signals being transmitted by the first component to the electronic system. The electronic switch produces output signals in response to the intercepted signals and transmits them to the second electronic component. The control circuit causes the electronic switch to switch from the first mode to the second mode. In the second mode, the electronic switch can transmit test signals from the control circuit to the second component.