Invention of the telephone useful and widespread apparatus it is now. The telephone exchange was an idea of the Hungarian engineer Tivadar Puskás (1844–1893) in 1876, while he was working for Thomas Edison on a telegraph exchange. Puskás was working on his idea for an electrical telegraph exchange when Alexander Graham Bell received the first patent for the telephone. This caused Puskás to take a fresh look at his own work and he refocused on perfecting a design for a telephone exchange. He then got in touch with the U.S. inventor Thomas Edison who liked the design. According to Edison, "Tivadar Puskas was the
Invention of the telephone "Mr. Watson, come here, I want to see you." and Watson answered. Bell tested Gray's liquid transmitter design in this experiment, but only after Bell's patent was granted and only as a proof of concept scientific experiment to prove to his own satisfaction that intelligible "articulate speech" (Bell's words) could be electrically transmitted. Because a liquid transmitter was not practical for commercial products, Bell focused on improving the electromagnetic telephone after March 1876 and never used Gray's liquid transmitter in public demonstrations or commercial use. Bell's telephone transmitter (microphone) consisted of a double electromagnet, in front of which a membrane,