History of mobile phones
A cellular telephone switching plan was described by Fluhr and Nussbaum in 1973, and a cellular telephone data signaling system was described in 1977 by Hachenburg et al.
Ernst Ruhmer
Ruhmer first gained widespread recognition for his work on improvements to Alexander Graham Bell's optical wireless telephone, the photophone. Bell introduced this device in 1880, which used selenium cells in the receiver to convert the fluctuating light produced by the transmitting unit into sounds. But Bell's invention only had a range of a few hundred meters, and he soon ended his research into this device. Ruhmer believed that the increased sensitivity of his selenium cells, combined with the superior receiving capabilities of professor H. T. Simon's "speaking arc", would make the photophone practical over longer signalling distances.