This document discusses various connectivity devices used in computer networks. It describes a transceiver as a device that can both receive and transmit signals. A repeater is used to regenerate incoming signals to maintain signal strength during transmission. A hub and switch are central devices in star networks that connect other devices, with the main difference being that a switch can deliver messages directly to the intended recipient while a hub broadcasts to all. A bridge connects two or more local area networks, while a router routes signals between similar networks and keeps routing information. A gateway interconnects dissimilar networks and is installed at the application layer.