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For constant nonzero voltage $V$, direct integration givesA constant electric potential difference therefore produces an oscillating pair electric current. The average of this ideal sinusoid over a complete cycle is zero; a measured nonzero steady electric current can include single-electron superconducting tunneling. Josephson's lecture explicitly separates the ordinary quasiparticle term from the phase-dependent term. ^[ref]

For an original numerical example, use the exact SI values $e=1.602176634\times 10^{-19}\mathrm{C}$ and $h=6.62607015\times 10^{-34}\mathrm{J}\mathrm{s}$. ThenThe corresponding period is about $0.2067834\mathrm{ns}$. These values describe an assumed exact applied voltage, not a historical measurement. The factor $2e$ identifies coherent pair transfer; replacing it by $e$ would halve the predicted frequency.

A superconducting weak link is a connection between regions with superconductivity whose coupling is weak enough that a substantial difference of quantum phase can develop across the connection. An insulating tunnel barrier is one realization; a narrow conducting constriction can also couple the regions. The current-phase relation of a superconducting weak link depends on the connection. A sinusoid is the leading tunnel-junction approximation, not a universal law for every superconducting weak link. ^[ref]