Abstract: An apparatus, a method, and a computer program product are provided for identifying signals in analogue electrical systems. The ID select signals that control the timing of this signal identification circuit comprise sequential numbers that count up and identify a corresponding signal. The signals to be identified are located on a group of input/output (I/O) pins. One multiplexer (first) selects a specific I/O pin in response to the ID select signals. An isolated voltage source is connected to this multiplexer and provides the selected signal to another multiplexer (second). The second multiplexer switches from this isolated voltage source to ground potential in response to the ID select signals. The isolated voltage source floats at the DC level of the selected I/O driver pin. Therefore, by connecting to the selected signal's I/O pin and the output of the second multiplexer, the selected signal can be identified and then probed.