At the International Telephone Exchange in London, switchboard operators patch calls to numerous continental destinations.

An engineer makes a routine test call over one of the continental lines. A cable ship sets out to locate and repair an apparent fault in one of the submarine telephone cables.

To locate the fault, two wires are played out over the stern of the ship as it follows the cable's course. Each wire has an electrode attached, and a galvanometer on the ship highlights when the fault has been reached. The navigating officer sets a zig-zag course over the cable to identify the precise point of the fault. When the galvanometer reaches its maximum level of deflection, a buoy is lowered, followed by a grappling hook to raise the cable. An officer sitting on the grappling hawser judges the moment when the cable is caught.

The cable repair team then takes over, sawing through the cable and pulling it aboard to identify the faulty part (very easy in this case, as it has become badly frayed). Once this has been cut out, the outside sheathing is removed. A jointer strips off the cover of the conductors and cleans them for soldering before joining them together in a vice. The new joint is insulated, the core covered, the sheathing wires spliced over the joint, and the splice lagged by wire.

The repaired cable is lowered back into the sea, and the work of the International Telephone Exchange can continue uninterrupted.