The repeater can connect the cables of two LANs, re-time and regenerate the digital signals on the cables, and then send them out. These functions are typical of the physical layer, the first layer in the OSI model. The function of the repeater is to increase the coverage area of the LAN. For example, the Ethernet standard stipulates that the maximum length of a single section of signal transmission cable is 500 meters. However, after connecting five sections of cables with the repeater, the maximum length of the signal transmission cable in the Ethernet can reach 2500 meters. Some brands of repeaters can connect cable segments with different physical media, such as thin coaxial cables and optical cables.

Repeater is a device that connects network lines and is often used for two-way forwarding of physical signals between two network nodes. The repeater mainly completes the function of the physical layer, is responsible for transmitting information bitwise on the physical layer of the two nodes, and completes the function of signal replication, adjustment and amplification to extend the length of the network. Due to the loss, the signal power transmitted on the line will gradually attenuate. When it attenuates to a certain extent, it will cause signal distortion, and thus lead to receiving error. The repeater is designed to solve this problem. It completes the connection of the physical circuit, amplifies the attenuated signal, and keeps the same as the original data. Generally, the two ends of the repeater are connected to the same media, but some repeaters can also complete the transfer of different media. Theoretically, the use of repeaters is unlimited, so the network can be extended indefinitely. In fact, this is impossible, because the network standard has specified the delay range of the signal, and the repeater can only work effectively within the specified range, otherwise it will cause network failure.