Just so i know i do understand this and i have read some topics i found on here with some good describtions by the serious guy in dark glasses (sorry cant remember username yet, damn newbies lol) The NIC listens on the network for any data already being transmitted, if there is some it waits, if it hears nothing it sends its data out. If at that time though another NIC does the same thing a collison occurs so both NIC's stop sending and wait a while. Now am i right in guessing they wait a random time? As if a collison occurs and the NIC wait a predetermed length of time surely the same collison will happen again , right? Also how exactly is a collison detected? Do the sent data packets get a recieved message come back so if there is a collison its not recieved and so the NIC knows , i doubt this as it would take ages surely, or do they bounce back, actually ill stop guessing and wait for the explaination ) Many thanks!