TestOut LabSim A+ Certification Practice Exam

To access the Internet via the Publicly Switched Telephone Network (PSTN), which device is essential?

1. Router

2. Switch

3. Modem

4. Network Interface Card

The correct answer is: Modem

In order to access the Internet through the Publicly Switched Telephone Network (PSTN), a modem is essential. A modem's primary function is to modulate and demodulate signals that allow digital data from a computer to be transmitted over analog phone lines. When a computer sends a transmission, it converts the digital signal into an analog signal that can be carried over the telephone line. Conversely, when data is received, the modem converts the analog signal back into a digital format for the computer. The other devices mentioned serve different roles in networking. A router directs traffic between different networks, allowing multiple devices to share a single Internet connection, but it does not handle the connection to the PSTN directly. A switch manages data flow between devices within a local area network, facilitating communication but not providing an Internet connection. The network interface card (NIC) allows a device to connect to a network, but again, it doesn't establish a link to the PSTN by itself. Thus, for connecting to the Internet via PSTN, the modem is the critical device that enables this communication.