We previously reported the construction, in 1921, of a radiotelephone link between California and  Santa Catalina Island, 26 miles across the sea (40 kilometers, for those in leaky old boats).  That link was in use for only two years, as reported here in the November 1923 issue of Popular Science.

In 1923, a cable was installed for both telegraph and telephone connections, both of which were multiplexed to allow multiple conversations.  One advantage of the new system, alluded to in the original article, was that radio conversations could be listened in to.  While some scrambling was put in place, the signals were transmitted over the air.  In addition, the radio license was surrendered, and that wavelength made available for broadcasting.