Which of these channel types produces a square calibration wave?

Which of these channel types produces a square calibration wave?

• A. EEG
• B. EMG
• C. Respiratory
• D. DC

Answer: (D)

Square calibration waves test how a channel handles fast transitions and overall gain and offset. A DC-coupled input preserves the zero-frequency component, so when the calibrator steps from one level to another, the waveform appears as a clean square with sharp edges. Other channels, like EEG, EMG, or respiratory, are typically AC-coupled or designed to measure slower, physiological signals; their conditioning paths smooth or filter out the rapid transitions, distorting a true square wave. Therefore, the square calibration waveform is produced on a DC channel because it can pass the abrupt step without distortion.

Square calibration waves test how a channel handles fast transitions and overall gain and offset. A DC-coupled input preserves the zero-frequency component, so when the calibrator steps from one level to another, the waveform appears as a clean square with sharp edges. Other channels, like EEG, EMG, or respiratory, are typically AC-coupled or designed to measure slower, physiological signals; their conditioning paths smooth or filter out the rapid transitions, distorting a true square wave. Therefore, the square calibration waveform is produced on a DC channel because it can pass the abrupt step without distortion.