WGU D413 – Telecommunications & Wireless Communications Objective Assessment | OA V1 and V2 | Questions and Answers | 2026 Update | 100% Correct.

1. Which layer of the OSI model is responsible for establishing, managing, and terminating sessions between two communicating hosts? a) Transport b) Session c) Presentation d) Application Answer: b) Session Explanation: The Session layer (Layer 5) is responsible for dialog control, establishing, managing, and tearing down sessions. The Transport layer handles end-to-end delivery, the Presentation layer handles data formatting, and the Application layer provides network services to user applications. 2. What is the primary characteristic of a half-duplex communication system? a) Data can be transmitted in both directions simultaneously. b) Data can be transmitted in both directions, but not at the same time. c) Data can only be transmitted in one direction. d) Data is transmitted in a broadcast format to all devices. Answer: b) Data can be transmitted in both directions, but not at the same time. Explanation: Half-duplex allows bidirectional communication, but the channel must be shared; devices must take turns transmitting and receiving (e.g., walkie-talkies). Full duplex allows simultaneous transmission (e.g., telephone), and simplex is one-way only (e.g., radio broadcast). 3. Which technology enables a single physical communication channel to be shared by multiple logical connections through the interleaving of data segments? a) Modulation b) Multiplexing c) Demodulation d) Attenuation Answer: b) Multiplexing Explanation: Multiplexing is the process of combining multiple data streams into one physical channel. Modulation is the process of varying a carrier signal to transmit data, and attenuation is the loss of signal strength. 4. In the context of telecommunications, what is the primary role of a protocol? a) To provide a physical medium for data transmission. b) To amplify the signal for longer distances. c) To define a set of rules for data exchange between devices. d) To convert digital signals to analog signals. Answer: c) To define a set of rules for data exchange between devices. Explanation: Protocols are formal standards that dictate the rules, syntax, semantics, and synchronization of communication. They ensure interoperability. Options a, b, and d describe physical media, repeaters/amplifiers, and modems, respectively. 5. What is the purpose of a checksum in a data transmission frame? a) To encrypt the data for security. b) To ensure the data is delivered to the correct application. c) To detect errors that may have occurred during transmission. d) To route the data to its destination. Answer: c) To detect errors that may have occurred during transmission. Explanation: A checksum is a value calculated from the data payload. The receiver performs the same calculation; if the values don't match, an error is detected, and the frame is typically discarded or a retransmission is requested. 6. Which of the following is a characteristic of a Wide Area Network (WAN)? a) It typically covers a small geographic area like a building. b) It is usually owned by the organization using it. c) It spans a large geographic area and often uses leased telecommunications circuits. d) It operates at a higher speed than a Local Area Network (LAN). Answer: c) It spans a large geographic area and often uses leased telecommunications circuits. Explanation: WANs are characterized by their large geographic scope (city, country, globe) and use of public or leased carrier services. LANs are typically privately owned, cover a small area, and offer higher speeds. 7. What is the fundamental difference between circuit-switched and packet switched networks? a) Circuit-switched is digital; packet-switched is analog. b) Circuit-switched establishes a dedicated path; packet-switched shares network resources. c) Circuit-switched is for voice; packet-switched is for data. d) Circuit-switched is slower; packet-switched is faster. Answer: b) Circuit-switched establishes a dedicated path; packet-switched shares network resources. Explanation: Circuit switching (like the traditional PSTN) creates a dedicated end-to-end connection for the duration of a call. Packet switching (like the Internet) splits data into packets that travel independently and share network resources, making it more efficient. 8. What is the key feature of Asynchronous Transfer Mode (ATM)? a) It uses variable-length packets. b) It is a connectionless protocol. c) It uses fixed-size cells of 53 bytes. d) It only operates over wireless media. Answer: c) It uses fixed-size cells of 53 bytes. Explanation: ATM uses fixed-size 53-byte cells (48 bytes payload, 5 bytes header). This allows for predictable, high-speed switching in hardware. It is a connection-oriented protocol that can carry voice, video, and data. 9. Which type of noise is caused by random electron movement in a conductor and is always present? a) Impulse noise b) Thermal noise c) Crosstalk d) Intermodulation noise Answer: b) Thermal noise Explanation: Thermal noise (or Johnson-Nyquist noise) is caused by the thermal agitation of electrons and is present in all electronic circuits. Impulse noise is a sudden spike, crosstalk is interference from another channel, and intermodulation occurs when signals mix nonlinearly.