Abstract: A portable general-purpose oscilloscope employs circuitry for receiving and converting serial digital video signals to composite and component analog signals via a digital to analog converter. The converted analog signals are applied to signal inputs of the oscilloscope for monitoring and display. Preferably, the oscilloscope is a digital phosphor oscilloscope. The oscilloscope control menus are arranged to control all of the usual functions of the oscilloscope and also to control the serial digital video circuitry. Apparatus is provided for storing data and waveforms. Circuitry is disclosed for deriving a trigger signal from a specific digital word of the serial digital bit stream. The trigger signal is applied to the trigger input terminal of the oscilloscope to allow the oscilloscope capture and display television waveform information around a unique occurrence of an event, as specified by the digital word.