Which circuit triggers the pulser and sweep circuits in an A-scan display?

• A. Clock
• B. Power supply
• C. Receiver amplifier
• D. Damping

Answer: (A)

The timing reference is what ties the emitted pulse to the display’s horizontal sweep. In an A-scan, you need the sweep to start exactly when the transducer fires so that echoes are plotted at the correct time after emission, corresponding to depth. The clock provides a steady, repeating trigger that starts both the pulser (to emit the pulse) and the sweep circuit (to move the trace across the screen) in lockstep. This synchronization keeps each scan consistent and properly scaled in time.

The other components don’t provide that triggering function: the power supply delivers voltage but not the timing signal to start a pulse and sweep; the receiver amplifier boosts the echoes for display; damping shapes the pulse to control ringing.