His past experience made him ready to work more with sound and electricity. He began his studies in 1874 with a musical telegraph, in which he used an electric circuit and a magnet to make an iron reed or tongue vibrate. One day, it was found that a reed failed to respond to the current. Mr. Bell desired his assistant, who was at the other end of the line, to pluck the reed, thinking it had stuck to the magnet. His assistant, Thomas Watson complied, and to his surprise, Bell heard the corresponding reed at his end of the line vibrate and sound the same - without any electric current to power it. A few experiments soon showed that his reed had been set in vibration by the changes in the magnetic field that the moving reed produced in the line. This discovery led him to stop using the electric battery current. His idea was that, since the circuit was never broken, all the complex vibrations of speech might be converted into currents, which in turn would reproduce the speech at a distance.