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What is a null modem and why is it needed?

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QUESTION POSED ON: 19 January 2005
What is a null modem and why is it needed?

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EXPERT RESPONSE
A null modem is a device that basically turns communications into two way communications through a straight wired connection. This is for half-duplex environments where you cannot send and receive on the same cable pairs at the same time (full-duplex). Basically, it swaps the send and receive pairs on one end so that the communication travels on one send pair, gets looped and travels back on the receive pairs.


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