A race-track microtron with a few beam orbits can be an alternative to a standard electron linear accelerator in a number of applications in which high beam power is not needed, like radiation therapy, industrial radiography or cargo inspection. In these cases the advantages of racetrack microtrons are low RF power consumption, and consequently low cost of the RF system, and a possibility of beam energy switch in a wide range by extracting the beam from different orbits. In the present work we describe the concept of a race-track microtron with pulseto- pulse beam energy switch in the range from 3.5 MeV to 9.5 MeV. Special attention is given to the optimization of the end magnets of a new type, which provide both the accelerating structure bypass and vertical beam focusing