What is the term for a method of combining multiple analog or digital signals into one signal over a transmission medium? This allows for a single medium, a limited physical resource to be shared between multiple users. The simplest example is several telephone calls carried over a single wire.

The method may be achieved by dividing frequencies - different signals are forwarded in distinct frequency ranges. It can also be achieved by using time to separate different data streams.

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Answer to yesterday's question: The device, so well known by its particular sound when connecting on home phone line, is called a "modem". Literal abbreviation from modulator-demodulator.

Early modems were devices using audible sounds in traditional telephone systems and leased lines. In the early stages async communication allowed around a few hundred bits per second. By 1990s the available bandwidth of telephone lines was exhausted with speeds reaching up to 56 kbit/s. Today, modems are largely invisible and capable of hundreds of megabites per second.