In 1925, the company publicly introduced a greatly improved system of electronic audio, including sensitive condenser microphones and rubber-line recorders (named after the use of a rubber damping band for recording with better frequency response onto a wax master disc). That May, the company licensed entrepreneur Walter J. Rich to exploit the system for commercial motion pictures; he founded Vitagraph, in which Warner Bros. acquired a half interest, just one month later. In April 1926, Warners signed a contract with AT&T for exclusive use of its film sound technology for the redubbed Vitaphone operation, leading to the production of "Don Juan" and its accompanying shorts over the following months. During the period when Vitaphone had exclusive access to the patents, the fidelity of recordings made for Warners films was markedly superior to those made for the company's sound-on-film competitors. Meanwhile, Bell Labs—the new name for the AT&T research operation—was working at a furious pace on sophisticated sound amplification technology that would allow recordings to be played back over loudspeakers at theater-filling volume. The new moving-coil speaker system was installed in New York's Warners Theatre at the end of July and its patent submission, for what Western Electric called the No. 555 Receiver, was filed on August 4, just two days before the premiere of "Don Juan".