Official websites use .gov

A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS

A lock () or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Figure 1a

Figure 1a: Waveform display of a 1.00 kHz sine wave over 5.0 milliseconds.

Waveform display of a 1.00 kHz sine wave over 5.0 milliseconds. Time is on the horizontal axis moving from left to right, and amplitude is on the vertical axis. The signal depicted is a pure sine wave with consistent positive and negative peaks at 1 decibel below their maximum possible values.