Vectorscope EV4161
A vectoroscope is a device designed to display a graph of the relationship of two signals. A vectoroscope is similar in principle to an oscilloscope operating in XY mode and is used in audio, video and television to visually monitor the relationship of two different signals.
Specialized vectoroscopes have various auxiliary elements on their display (for example, vectoroscopes for monitoring video signal parameters have a grid indicating the location of signal parameters), as well as built-in demodulators and demultiplexers to simplify operation.