By looking at the Josephson equations, we see that a positive constant, then just increases linearly without bound.
Therefore, from the first equation: .
This meas that we can use a Josephson junction as a perfect voltage to frequency converter.
Wikipedia mentions that this frequency is , so it is very very high, so we are not able to view individual points of the sine curve separately with our instruments.
Also it is likely not going to be very useful for many practical applications in this mode.
An I-V curve can also be seen at: Figure "Electron microscope image of a Josephson junction its I-V curve".