What is a modem? A modem (from modulate and demodulate) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from driven diodes to radio. Experiments have even been performed in the use of modems over the medium of two cans connected by a string.[citation needed].
Speed: The speeds of modems can vary. For example, modems remained at 300 and 1200 bit/s into the mid 1980s.
What is the most recent standard of traditional modems? The lastest version is V.92.
What is ADSL? Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. It does this by utilizing frequencies that are normally not used by a voice telephone call, in particular, frequencies higher than normal human hearing. This signal will not travel very far over normal telephone cables, so ADSL can only be used over short distances, typically less than 5 km. Once the signal reaches the telephone company's local office, the ADSL signal is stripped off and immediately routed onto a conventional internet network, while any voice-frequency signal is switched into the conventional phone network. This allows a single telephone connection to be used for both ADSL service and voice calls at the same time.
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