Which hardware device enables the connection of serial devices across a network?

The terminal server is the correct choice because it specifically enables the connection and management of multiple serial devices over a network. This device acts as a bridge between serial devices and the network, allowing these devices, often used in industrial or legacy systems, to communicate over Ethernet or IP networks.

Terminal servers convert the data from the serial devices into a format that can be transmitted over the network, facilitating communication between the devices and computers on the network. This functionality enables centralized management and monitoring of the serial devices, making them accessible even if they are physically distant from the main network.

In comparison, a modem primarily facilitates internet connectivity by converting digital data to analog signals (and vice versa) for transmission over phone lines or other media. A network switch operates at the data link layer and is used to connect various devices within a local area network (LAN), directing traffic between them but not specifically tailored for serial device management. A router connects different networks, directing data packets between them, but does not inherently provide the specific connectivity features required for serial devices.