How did granville woods change the telegraph in 1887

Woods's most important invention was the multiplex telegraph, also known as the "induction telegraph," or block system, in 1887. The device allowed men to communicate by voice over telegraph wires, ultimately helping to speed up important communications and, subsequently, preventing crucial errors such as train accidents. Woods defeated Thomas Edison's lawsuit that challenged his patent, and turned down Edison's offer to make him a partner. Thereafter, Woods was often known as "Black Edison."