Initially, the telephone system tended to follow telegraph practice but the requirements were different. Telegraphs were usually long-distance circuits with lines from town to town, whereas in the early days of the telephone, calls were usually between subscribers fairly close together in a congested urban area. Bare wires strung over rooftops were the usual practice at first, and the circuits used earth return, but crosstalk was a serious problem and two-wire circuits were soon introduced. At first, the most commonly used wire was galvanized iron. Its high electrical resistance was a great disadvantage, but it was some years before hard-drawn copper, with adequate tensile strength, became available. Now, we are moving rapidly into an era of computerized exchanges connected by optical fibers. Bell would hardly recognize the system today, but we rightly salute him as the man who began it by first transmitting speech by electricity.