*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 signal into discrete time slots. Each signal is assigned a specific time slot in a repeating sequence, allowing multiple signals to share the same channel without interference.

### Explanation:

1. **Correct Answer (B):**  
   - **Two or more signals are arranged to share discrete time slots of a data transmission.**  
     In TDM, each signal is given a specific time slot in which to transmit its data. This allows multiple signals to be sent over the same channel by interleaving them in time. The signals are synchronized so that each one knows when its time slot occurs.

2. **Why Other Choices Are Incorrect:**

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

   - **Choice C:**  
     - **Two or more data streams share the same channel by transmitting time of transmission as the sub-carrier.**  
       This is not a correct description of any standard multiplexing technique. TDM does not use the time of transmission as a sub-carrier; it uses time slots.

   - **Choice D:**  
     - **Two or more signals are quadrature modulated to increase bandwidth efficiency.**  
       This describes quadrature amplitude modulation (QAM) or similar techniques, which are not related to TDM. These techniques use phase and amplitude variations to encode data, not time slots.

### Key Points:

- **TDM** is about dividing time, not frequency or phase.
- Each signal in TDM gets a unique time slot, ensuring no overlap.
- TDM is efficient for digital signals where precise timing can be maintained.