Apparatus and methods for identifying a signal on a printed circuit board (‘PCB’) under test, including an integrated circuit mounted on the PCB, the integrated circuit having a test signal generator that transmits a test signal to an output pin of the integrated circuit, with the output pin connected to a test point on the PCB; the integrated circuit also having signal identification logic that inserts into the test signal, an identifier of the signal; a test probe in contact with the test point; and a signal-identifying controller that receives the test signal and the identifier from the test probe and displays, in dependence upon the identifier, the identity of the signal.