In a basic pulse-echo ultrasonic instrument, the component that coordinates the action and timing of other components is called:

• A. Display unit or CRT
• B. Receiver
• C. Marker circuit or range marker circuit
• D. Synchronizer, clock, or timer

Answer: (D)

Coordinating the action and timing of pulsing, receiving, and display in a pulse-echo ultrasonic instrument is done by the synchronizer, clock, or timer. This timing circuit provides a common reference that drives when the transmitter fires and when the receiver opens to listen for echoes, ensuring echoes from a specific depth are sampled in the correct time window. It also sets the time base that converts elapsed time into display depth, so the sweep and depth calibration stay consistent. Because of this central timing role, all parts work in sync: the pulser, the receiver, and the display respond in coordinated harmony. The other components perform supportive tasks—display shows results, receiver processes and amplifies echoes, and the marker circuit highlights a depth—without managing the overall timing of the system.