Schmitt-trigger conditioning of a 60 Hz reference: In a digital clock front-end, a 60 Hz mains-derived waveform is passed through a Schmitt-trigger buffer to create clean logic transitions at the rate of ________.

Introduction / Context:
Digital clocks often derive timing from either a crystal oscillator or the AC mains frequency (50/60 Hz). When using the mains, the sinusoidal voltage must be isolated, scaled, and squared up into clean logic pulses. A Schmitt trigger provides hysteresis to convert the slowly changing waveform into sharp digital edges.

Given Data / Assumptions:

• Input frequency is 60 Hz.
• A Schmitt trigger outputs rail-to-rail logic-level pulses on threshold crossings.
• No frequency division or multiplication is performed in the Schmitt stage itself.

Concept / Approach:
The Schmitt trigger does not change the fundamental frequency; it improves edge quality and noise immunity. Therefore, its output toggles at the same rate as the input fundamental, producing a pulse train at 60 pulses per second (pps), suitable for gating counters or for further division to 1 pps.

Step-by-Step Solution:

Verification / Alternative check:
Oscilloscope captures show one complete output cycle per 60 Hz input cycle after the Schmitt stage.

Why Other Options Are Wrong:

Common Pitfalls:
Mislabeling Schmitt outputs as sine pulses; ignoring isolation and safety when sampling the mains waveform.

Final Answer:
60 pps