What is the primary purpose of a jam signal in a contention-based MAC system like Ethernet?

In a contention-based MAC (Media Access Control) system like Ethernet, the primary purpose of a jam signal is to indicate that a collision has occurred on the network. When multiple devices attempt to send data at the same time, their signals can overlap, leading to a collision. This is where the jam signal comes into play.

Once a device detects that a collision has happened, it will send out a jam signal. This signal serves two major functions: it informs all participating devices that a collision occurred, prompting them to stop transmitting, and it also allows them to take appropriate action, such as waiting a random amount of time before attempting to retransmit. This helps reduce the likelihood of future collisions and ensures orderly access to the network.

Other options are not correct in this context. Enhancing signal strength is unrelated to the function of a jam signal, as is improving bandwidth. Initiating a data transfer is also not a role played by the jam signal; rather, it is a notification mechanism for managing access to the network medium under contention scenarios.