The vector model is a way of visualising some aspects of NMR by following the magnetisation vector in Cartesian space. This is explained in the lectures of James Keeler which can be found both as a video and a pdf. This model is a non-quantum mechanical description of the result of the application of radiofrequency pulses. It involves similar geometric explanations and allows for easy understanding of the basic principles of pulse sequences. Although the vector model can only be applied to uncoupled spins it does enable the demonstration of principles such the pulse acquire mechanism by which the NMR signal is generated and also the mode of action of the spin echo.