Data Transmission And Communication : MCQs & PYQs with Explanation

Option B

A Half-Duplex connection allows communication in both directions, but only one direction at a time. When one device is transmitting data, the other device must wait until the transmission is finished before sending data.
For example, in a walkie-talkie, both persons can communicate with each other, but they cannot normally speak at the same time. One person speaks while the other listens, and then they switch roles.

Option D

Industrial, Scientific, and Medical (ISM) bands are portions of the radio spectrum reserved internationally for non-commercial purposes like industrial heating, medical equipment, and scientific experimentation. Over time, they have also been widely used for unlicensed wireless communication, such as Wi-Fi and Bluetooth.

Option C

Manchester Encoding is a digital line‑coding scheme used at the physical layer to transmit data along with clock information. Each bit period is split into two phases, and there is always a transition in the middle of the bit, which provides self‑clocking and helps the receiver stay synchronized.
So, Manchester Encoding is used in the Physical Layer and provides signal synchronization through frequent transitions. It is called a Biphase Code because each bit has two phases, and its required transition occurs at the center of the bit, not necessarily at the bit boundary.

Option A

A scrambler is used in line coding schemes to modify the original data before transmission.

• To remove long sequences of 0s or 1s which can cause synchronization problems.
• To make the transmitted data appear random, even if the original data has patterns.
• Helps in maintaining clock synchronization between sender and receiver.

Option B

A coaxial cable consists of multiple layers designed to transmit signals efficiently with minimal interference. Its construction includes:

• A solid inner conductor (usually copper) to carry the signal.
• An insulating layer (dielectric) surrounding the conductor.
• An outer conductive sheath (shield) to protect against noise and interference.
• Often an outer protective jacket.

Option D

Digital Data Transmission is considered more secure because the data can be encrypted before transmission. Encryption converts the original information into a coded form so that unauthorized users cannot easily understand or access the data.
In digital communication systems, techniques such as encryption, encoding, and authentication are commonly used to improve security during data transfer.

Option C

In Circuit Switching, a dedicated communication path is established between two stations before data transfer begins. This path remains reserved for the entire duration of the communication, ensuring a continuous and reliable connection. A common example is the traditional telephone network.

• Packet Switching does not use a dedicated path, data is sent in packets that may take different routes.

Option C

Encoding schemes in Ethernet convert data bits into transmittable symbols over physical media (fiber/copper). They ensure clock recovery (frequent transitions), DC balance (equal 0s/1s), and error detection by adding overhead bits.
In Gigabit Ethernet (1000BASE-X), data transmission uses an encoding scheme to ensure reliable communication, proper synchronization, and error detection. The scheme used is 8B/10B encoding.
In this technique, 8 bits of actual data are converted into 10-bit code groups before transmission. This extra 2 bits help in:

• Maintaining signal balance (DC balance).
• Providing clock synchronization.
• Detecting transmission errors.

Therefore, 1000BASE-X uses 8B/10B encoding, where 8-bit data is converted into 10-bit groups for reliable high-speed transmission.

Option D

In satellite communication, signals travel between the earth station and the satellite using different frequencies. There are two main communication links:

• Uplink : Transmission from earth station to satellite.
• Downlink : Transmission from satellite to earth station.

The frequency used for sending signals from the satellite to the earth station receiver is called the Downlink Frequency.
For example, a TV broadcast satellite sends signals to home dish antennas using downlink frequency.

Option D

When a signal travels through a communication medium such as a cable, optical fiber, or wireless channel, its energy gradually decreases as it travels over a distance.
This loss or reduction in signal strength is called Attenuation. Attenuation generally increases as the distance of transmission increases. It is commonly measured in decibels (dB).