Meantime, the telephonic art in America was undergoing very rapid development. In March, 1878, addressing "the capitalists of the Electric Telephone Company" on the future of his invention, Bell outlined with prophetic foresight and remarkable clearness the coming of the modern telephone exchange. Comparing with gas and water distribution, he said: "In a similar manner, it is conceivable that cables of telephone wires could be laid underground or suspended overhead communicating by branch wires with private dwellings, country houses, shops, manufactories, etc., uniting them through the main cable with a central office, where the wire could be connected as desired, establishing direct communication between any two places in the city.... Not only so, but I believe, in the future, wires will unite the head offices of telephone companies in different cities; and a man in one part of the country may communicate by word of mouth with another in a distant place." All of which has come to pass. Professor Bell also suggested how this could be done by "the employ of a man in each central office for the purpose of connecting the wires as directed." He also indicated the two methods of telephonic tariff--a fixed rental and a toll; and mentioned the practice, now in use on long-distance lines, of a time charge. As a matter of fact, this "centralizing" was attempted in May, 1877, in Boston, with the circuits of the Holmes burglar-alarm system, four banking-houses being thus interconnected; while in January of 1878 the Bell telephone central-office system at New Haven, Connecticut, was opened for business, "the first fully equipped commercial telephone exchange ever established for public or general service."