(1) The result of two work stations trying to use a shared Transmission medium (cable) simultaneously (overlapping). The electrical signals, which carry the information they are sending, bump into each other (a collision). This ruins both signals (interference) meaning they both have to retransmit their information. In most systems, a built in delay will make sure the collision does not occur again. The whole process takes fractions of a second. Collisions in LANs make no sound. (2) A collision is a condition where two devices detect that the Network is idle and end up trying to send packets AT exactly the SAME time (within 1 round-trip delay). Since only one device can transmit at a time, both devices must back off and attempt to retransmit again.