reflected the organization of the network schedule, which was divided into 15 minute program blocks. In addition, effective May 11, 1927, the Federal Radio Commission's General Order No. 8 specified that each station was "directed to announce its call letters and location... not less than once during each 15 minutes of transmission". The use of the NBC chimes as network switching cues eventually allowed the network to save money on infrastructure costs. Until 1933 it was common practice to run a second line that used telegraphic signalling to provide networking communication. After that date the normal policy was to eliminate this second line and send the networking cues over the program lines. Information about the early development of the NBC chimes is very sparse, although work began shortly after the first NBC network broadcast on November 15, 1926. A 1950 internal NBC memo, "NBC Chimes: First Use of the famous NBC Chimes", states that "The use of chimes for identifying NBC was first conceived by Phillips Carlin," and this memo has a timeline entry for December 22, 1926 that states: "Chimes purchased from Lesch Co for $48.50". Phillips Carlin was a well-known NBC announcer, who had experience employing chimes in radio broadcasts dating back to at least 1924. At that time he was the announcer for the Silvertown Chimes program, which was broadcast over the "WEAF chain" network originating in New York City. (WEAF was owned by the American Telephone & Telegraph Company (AT&T). In 1927, after the RCA bought out AT&T's radio operations, the WEAF chain was reorganized as the NBC Red Network.) A contemporary review of this show noted that each program opened with "the soft ringing of chimes", followed by Carlin's announcement that "The Silvertown Chimes have rung out their greeting. Each week they have announced an hour of music, a program of dance so delightful that it drives all thoughts of care away." A 1942 NBC account of the origin of the chimes gave additional credit for their refinement to NBC chief engineer O. B. Hanson and Ernest LaPrade, an NBC orchestra leader. This account also states that there was an ongoing evolution during the developmental period, as the chime sequence originally consisted of seven notes, which, according to Ernest LaPrade, proved difficult to play correctly, so the sequence was shortened to five, then four, and finally three notes. The notes were manually played on four-bar