Final answer:
The devices that can serve as a demarcation point include a modem and a media converter, which are points where responsibility for the connection shifts from service provider to user.
Step-by-step explanation:
The devices that can be used as a demarcation point include a modem and a media converter. A demarcation point is the physical point at which the public network of a telecommunications company ends and the private network of the customer begins. This is the location where the responsibility for the connection changes hands from the service provider to the user. It is also where network troubleshooting typically divides tasks between customer-maintained equipment and provider-maintained equipment.
A modem (modulator-demodulator) serves as a demarcation point by converting digital signals from a user's computer into analog signals that can be transmitted over telephone lines or other communication media, and vice versa for incoming signals. A media converter is a device used to interconnect different types of media, such as converting electrical signals on copper cables to optical signals for fiber optic cables, and can serve as a demarcation point between the service provider's fiber-optic infrastructure and a customer's copper-based infrastructure.
A router or a switch typically goes beyond the demarcation point, managing data flow within the customer's private network, so they are not usually considered as demarcation devices.