Which device converts electronic signals into visual displays, such as pictures and waveforms?

The device that converts electronic signals into visual displays, such as pictures and waveforms, is the oscilloscope. An oscilloscope allows users to visualize electrical signals in a way that can be readily interpreted, providing a graphical representation of voltage over time. This capability is crucial for observing the characteristics of signals in various applications, including electronics, telecommunications, and medical diagnostics.

While a cathode ray tube (CRT) can be part of an oscilloscope and is itself a display technology, it does not perform the function of converting signals independently. The CRT displays the information generated by the oscilloscope but is not the primary device that interprets and converts electrical signals into visible forms. In contrast, the oscilloscope takes those electronic signals and presents them in a format that allows for analysis and measurement.

The resolver and phase shift device do not serve this purpose. A resolver is an electromechanical device used for measuring angular positions, while a phase shift device is used to alter the phase of a signal rather than visualizing it. Thus, the oscilloscope is the correct choice because it specifically combines input signals with display technology to create visual representations of those signals.