*Question G7C13:
What term specifies a filter’s maximum ability to reject signals outside its passband?*  

*Correct Answer is  D: Ultimate rejection*  

### AI Response: (may contain errors)  

In the context of filters, the term "ultimate rejection" refers to the filter's maximum ability to reject signals outside its passband. This is the correct answer because it specifically describes the filter's performance in attenuating unwanted frequencies that are far from the passband.

### Explanation:

1. **Ultimate Rejection (Correct Answer):**  
   - **Definition:** Ultimate rejection is the measure of how well a filter can attenuate or reject signals that are outside its passband, particularly at frequencies far removed from the passband edges.
   - **Importance:** It indicates the filter's effectiveness in preventing unwanted signals from passing through, which is crucial in reducing interference.

2. **Why the Other Choices are Incorrect:**

   - **Notch Depth:**  
     - **Definition:** Notch depth refers to the amount of attenuation at a specific frequency within a notch filter's stopband.
     - **Reason for Incorrectness:** It is specific to notch filters and does not describe the overall rejection capability of a filter outside its passband.

   - **Rolloff:**  
     - **Definition:** Rolloff describes how quickly a filter transitions from the passband to the stopband, typically measured in dB per octave or dB per decade.
     - **Reason for Incorrectness:** It relates to the steepness of the filter's transition band, not the maximum rejection capability.

   - **Insertion Loss:**  
     - **Definition:** Insertion loss is the loss of signal power resulting from the insertion of a filter in a transmission line, measured within the passband.
     - **Reason for Incorrectness:** It pertains to the loss of signal within the passband, not the rejection of signals outside the passband.

### Summary:

- **Ultimate Rejection** is the key term for describing a filter's ability to reject out-of-band signals.
- Other terms like **notch depth**, **rolloff**, and **insertion loss** describe different aspects of filter performance and do not address the maximum rejection capability.