Monostable multivibrator at rest — what is the typical Q output level before any trigger? Assume standard TTL/CMOS one-shot behavior where the output goes active for a timed pulse and then returns.

Introduction / Context:
A monostable multivibrator has one stable state. When idle (no trigger), the output sits in that state; a trigger forces a temporary transition for a timed duration. This question checks default logic level knowledge for common one-shot outputs.

Given Data / Assumptions:

• Standard one-shot where the timed pulse is a HIGH pulse at Q.
• After timing, the device returns to its stable state.

Concept / Approach:
Most textbook one-shots are depicted with Q LOW at rest and a positive-going pulse on trigger. Although some devices offer inverted outputs or alternative wiring, the conventional Q output idles LOW and pulses HIGH.

Step-by-Step Solution:

Verification / Alternative check:
Diagrams for 555 monostable and 74x121/123 families commonly show Q LOW at rest, going HIGH for t = K * R * C, then returning LOW.

Why Other Options Are Wrong:

• +5 V or HIGH: that would imply a LOW-going pulse, not the typical default.
• SET: descriptive but not a logic level.
• Hi-Z: outputs are driven, not tri-stated, in basic one-shots.

Common Pitfalls:

• Confusing Q with /Q (inverted output), which would idle HIGH.

Final Answer:
LOW