jam

In an Ethernet network, a jam is a signal from one device to all other devices that a collision has occurred. Specifically, the device was trying to send a frame while another device was also trying to put a frame on the line). The jam signal results in additional collisions in any other frames in process of being put on the line and warns non-transmitting devices to wait. Effectively, a jam provides a way to force all devices to restart any bids to get control of the line.