Video colour component isolation circuitry

A circuit and method for electrically isolating an analog colour component signal of a video signal are described. A first path 144 receives the colour component signal and includes an optical isolator 158 which passes the colour signal over a first frequency range extending from DC. A second path 146 also receives the colour component signal and includes a transformer 183 which passes the colour signal over a second frequency range extending from above DC. A summing device 190 sums the outputs of the first and second paths to produce an output colour component signal. The first path and second path are configured to provide a substantially constant amplitude for the output signal over the first and second frequency ranges and a substantially constant phase relationship between the colour component signals in the first and second paths at the overlap between the first and second frequency ranges.