  We present an electronic circuit whose dynamical properties emulate those of
a resistively and capacitively shunted Josephson junction (RCSJ). We show how
it reproduces the switching properties of a shunted junction and its dependence
on the quality factor. A thermal noise source is then used to characterize the
temperature dependence of the phase dynamics. In the presence of an AC drive,
phase locking is observed at integer and rational multiples of the drive
frequency, and it competes with chaotic behavior when the quality factor of the
junction exceeds unity. We characterize the stability of phase-locked and
chaotic states in the presence of thermal noise.
