Until Thomas Alva Edison tackled the problem of multiple telegraph messages, the most that could be sent over one wire at a time was two. Edison increased the number to four. Later, Western Union engineers developed the "Multiplex" system which enabled them to transmit four communications simultaneously in each direction. "Voice carrier" currents of different frequencies, in Multiplex groups of four, recently made possible 32 messages in each direction over a four-wire circuit. Last week, Western Union announced that an electrical tone generator borrowed from a musical instrument had tripled the...
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