Deep Dive: E6C07
The correct answer is B: A resistor connected to the positive or negative supply used to establish a voltage when an input or output is an open circuit. What best describes a pull-up or pull-down resistor is a resistor connected to the positive or negative supply used to establish a voltage when an input or output is an open circuit. Pull-up/pull-down resistors set default voltage levels. For amateur radio operators, this is important for digital circuits. Understanding this helps when designing digital circuits.
Why Other Answers Are Wrong
Option A: Incorrect. Resistor in keying circuit to reduce key clicks isn't pull-up/pull-down - pull-up/pull-down establishes voltage when open. Keying circuit isn't the description. Option C: Incorrect. Resistor ensuring oscillator frequency doesn't drift isn't pull-up/pull-down - pull-up/pull-down establishes voltage when open. Oscillator isn't the description. Option D: Incorrect. Resistor connected to op-amp output preventing signals exceeding supply isn't pull-up/pull-down - pull-up/pull-down establishes voltage when open. Op-amp output isn't the description.
Exam Tip
Pull-up/pull-down resistor = resistor connected to supply to establish voltage when input/output is open. Think 'P'ull-'U'p/'P'ull-'D'own = 'P'rovides 'D'efault voltage. Pull-up/pull-down resistors set default voltage levels. Not keying circuit, not oscillator, not op-amp output - just establishes voltage when open.
Memory Aid
Pull-up/pull-down resistor = resistor connected to supply to establish voltage when input/output is open. Think 'P'ull-'U'p/'P'ull-'D'own = 'D'efault voltage. Pull-up/pull-down resistors set default voltage levels. Important for digital circuits.
Real-World Example
A pull-up or pull-down resistor: It's a resistor connected to the positive or negative supply used to establish a voltage when an input or output is an open circuit. This ensures a defined logic level when the circuit is floating. This is the description - establishes voltage when open.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E6C
Reference: 2024-2028 Question Pool · E6 - Circuit Components
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E6C topic.