In 1935, Soviet Central Scientific Research Institute of Communications received a government order to design the "Speaking Clock" for Moscow City Telephone Network. "Speaking Clock" was constructed based on cinematic techniques and consists of discs with pulse-density modulation optical marks on photographic tapes, photocell with actuator, and audio tube amplifier. On May 14, 1937 "speaking clock" connected to Moscow City Telephone Network for test operation and it was reachable on the numbers and . It was speaking with the recorded voice of Soviet actor and broadcaster Emmanuil Tobiash. In 1937, the first cities to be equipped with this devices were Moscow and Leningrad.