Cisco Console Port

Console Session on cisco router

Hi                I have two routers in my lab , which  is not accessible via console. one is a cisco 3640 router, it shows some unrecognised characters when accessing via console. i did reset the baud rate jumper ,but no result.               In 2811 router it shows boot...

Cable required - Cisco 2811

I need to know the type of cable to login to cisco 2811 router. Can i use the LAN port on my laptop, use a straight cable and connect through the console port of the router? Please help