I saw in a documentation that deals with the testing of valve circuits a device called vectorscope. Is it the same thing as an oscilloscope?
No, the vectorscope is an instrument similar to the oscilloscope, as it uses a cathode ray tube, but it has inputs for the X and Y axes, providing an image that is the composition of the signals from the two inputs, that is, it does not have scan. A typical oscilloscope can work in vector mode if we put it in X-Y mode by taking scans. In the figure we have the aspect of one of these instruments. It is also called a waveform monitor.