Abstract: A nonlinear electronic circuit is used to demonstrate important dynamical properties of nonlinear oscillators. The apparatus is well suited for use in an undergraduate instructional laboratory since it reliably generates high-quality data and is inexpensive, compact, and simple to assemble. No special equipment is required other than the unijunction transistor on which the RLC-like circuit is based. Properties of spontaneous and driven nonlinear oscillators, such as unstable foci, stable limit cycles, and entrainment, can be experimentally investigated conceptually and quantitatively with this circuit. Experimental objectives for short-term and lon-term projects are suggested.