Which device is essential for connecting a coaxial cable to a modem?

A splitter is essential for connecting a coaxial cable to a modem because it allows multiple signals to be transmitted over a single coaxial line. In many setups, a single coaxial cable may need to split the signal from the wall outlet to feed both a modem and a cable box or additional devices. The splitter ensures that the signal is distributed effectively without degrading the quality of the internet connection to the modem.

While a router can provide wireless access for devices connected to the network, it does not directly handle the connection between the coaxial cable and the modem. An Ethernet switch is used to connect multiple devices on a local network using Ethernet cables, but it does not interact with the coaxial cable itself. A modulation device, which could refer to a type of modem, is relevant for converting signals but is not what connects the coaxial cable directly to the modem. Thus, the splitter is the critical component that facilitates this connection.