*Question E8B11:
What is digital time division multiplexing?*  

*Correct Answer is  B: Two or more signals are arranged to share discrete time slots of a data transmission*  

### AI Response: (may contain errors)  

Digital time division multiplexing (TDM) is a method used to transmit multiple signals over a single communication channel by dividing the time into discrete slots. Here’s a breakdown of the correct answer and why the other options are incorrect:

### Correct Answer: 
**B: Two or more signals are arranged to share discrete time slots of a data transmission.**

- **Explanation**: In TDM, each signal is assigned a specific time slot during which it can transmit its data. This allows multiple signals to share the same channel without interference, as each signal only uses the channel during its designated time slot. This method is efficient for digital communications, as it maximizes the use of available bandwidth.

### Why the Other Choices are Incorrect:

- **A: Two or more data streams are assigned to discrete sub-carriers on an FM transmitter.**
  - **Explanation**: This describes frequency division multiplexing (FDM), not TDM. In FDM, different signals are transmitted simultaneously on different frequency sub-carriers, rather than sharing time slots.

- **C: Two or more data streams share the same channel by transmitting time of transmission as the sub-carrier.**
  - **Explanation**: This statement is misleading. While it mentions sharing a channel, it incorrectly implies that time of transmission is treated as a sub-carrier. TDM does not use sub-carriers; it strictly divides time into slots for each signal.

- **D: Two or more signals are quadrature modulated to increase bandwidth efficiency.**
  - **Explanation**: This describes a technique related to quadrature amplitude modulation (QAM) or phase shift keying (PSK), which is a different method of multiplexing. It does not involve time slots but rather modulates signals to occupy the same frequency band.

### Summary:
- TDM is characterized by the allocation of time slots for each signal, allowing multiple signals to share the same channel without interference.
- Remember that TDM is distinct from FDM and modulation techniques like QAM or PSK, which operate on different principles.

This understanding will help you differentiate between various multiplexing techniques on the exam.