  We present experimental and numerical results from a real-time detection of
time-correlated single-electron tunneling oscillations in a one-dimensional
series array of small tunnel junctions. The electrons tunnel with a frequency
f=I/e, where I is the current and e is the electron charge. Experimentally, we
have connected a single-electron transistor to the last array island, and in
this way measured currents from 5 fA to 1 pA by counting the single electrons.
We find that the line width of the oscillation is proportional to the frequency
f. The experimental data agrees well with numerical simulations.
