What is a modem?

While broadband connections have made computer OEMs remove the modem from the motherboards, there are still a few applications that could use the modem characteristics. This article will review the device and its possibilities.

What it is?

Definition
A modem is a digital device that sends digital signals through an analog interface. It modulates the analog wave form to insert the digital data, and it can demodulates the information carried by this signal into digital contents. Modulation and demodulation The modulation - demodulation of the signal was made traditionally with telephone lines over copper wire, which had come technical limitations. The carrier sinus wave was limited (because of power loss over distance) to 1,650 Hertzs, but some digital tricks allowed for the transmission of 9,600, 14,400, 28,800 and up to 56,600 kilobits of information per second. Slow transfer rate and broken communication As per today's speed, that transfer rate was too slow, and communication was broken (and the message corrupt) if there was any issue in the line (clics, phone hung). However, it was enough for some applications that may still be useful nowadays. As a result, in the market there are many modems with USB connection to update modern computers with that communication tool.

What it is for

Of course, the clear applications are the ones related to the telephone service itself. You may forget about high-speed video. Main uses would be: - Machine to machine communication: for low-speed, remote control of some devices - for example, transformer or switch stations. - Fax communication: A modem will transform your computer in a fax machine, both to send (in a process similar to printing, but indicating a phone nuber) and to receive (in bitmap format, that can be translated into text, image or PDF). - Answering machine: you may program your computer to take care of your incoming calls, and even a record function may be provided. Of course, you may record our own incoming call message. Further services (automated calling machine, data services) may only be available in certain countries - and they may not be legal in yours. In all cases, you should try to have a modem speed high enough for your intended application. A modem with 56k will be surely the best option. Simultaneously, bi-directional communication (duplex mode) would also be desired.