As early as 1877, Erenst Verner of Germany's Siemens Company obtained a patent for a moving coil horn according to Fleming's left-hand law. In 1898, Sir Oliver Lodge of England further invented the cone horn based on the principle of the telephone microphone, which was very similar to the modern horn we are familiar with. Sir Lodge called it "the roaring telephone". However, this invention cannot be used, because the triode vacuum tube was not invented until 1906 by Lee De Forest, and it was several years later that a usable amplifier was made, so the cone speaker did not become popular until the 1930s.