The title is potentially misleading. Voice communication by radio had been performed since about 1906 (Lee de Forest and, more likely, Reginald Fessenden, both

The title is potentially misleading. Voice communication by radio had been performed since about 1906 (Lee de Forest and, more likely, Reginald Fessenden, both making claims) and was approaching routine by the 1920s. (The station that is now WWJ in Detroit had been broadcasting the daily news by AM voice for over a year when this RCA facility was commissioned.) This was the first commercial installation to relay phone traffic by radio internationally.