How Do I Reverse Telnet

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I have 3 different networks running to my site that do not touch each other at all. I only have access to one from my office. My buddy told me that it's possible to connect a rollover cable to the switches so that I can telnet into all 3 networks but traffic will not pass between them. I know that I need a rollover cable and that I have to connect it to the Con and Aux ports but after that I'm lost. Can anyone help me out with a step by step on how to do it. I have 3 cisco 3550's sitting in a box in a bunch of different offices.