Deep Dive: E8B11
The correct answer is B: Two or more signals are arranged to share discrete time slots of a data transmission. Digital time division multiplexing (TDM) is when two or more signals are arranged to share discrete time slots of a data transmission. Each signal gets a specific time slot in a repeating sequence. In TDM, time is divided into slots, and each signal is assigned specific slots. The signals take turns using the channel - signal 1 uses slot 1, signal 2 uses slot 2, signal 1 uses slot 3, etc. This allows multiple signals to share the same frequency channel by using different time periods. TDM is widely used in digital communication systems. It's efficient because all signals can use the full bandwidth during their assigned time slots.
Why Other Answers Are Wrong
Option A: Incorrect. Assigning data streams to discrete sub-carriers on an FM transmitter describes frequency division multiplexing, not time division multiplexing. Option C: Incorrect. Sharing a channel by transmitting time of transmission as the sub-carrier doesn't describe TDM. TDM uses time slots, not time information as a subcarrier. Option D: Incorrect. Quadrature modulation increases bandwidth efficiency but doesn't describe time division multiplexing. TDM uses time slots, not quadrature modulation.
Exam Tip
TDM = Time slots for each signal. Remember: Digital time division multiplexing arranges two or more signals to share discrete time slots. Each signal gets specific time periods in a repeating sequence.
Memory Aid
**T**DM = **T**ime **S**lots (think 'TDM = TS' = Time Slots)
Real-World Example
You're using a digital system with multiple users. Each user is assigned specific time slots - user 1 transmits in slots 1, 4, 7..., user 2 transmits in slots 2, 5, 8..., etc. This is TDM - the signals share the same frequency channel by using different time periods. All users can use the full bandwidth during their assigned slots.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E8B
Reference: FCC Part 97.3
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E8B topic.