All infrared night vision devices are designed to automatically short-power when not in use, and only start to supply energy when the start switch is pressed. The binocular device has an "on/off" switch that requires the user to turn off the device when finished. If a certain "humming" sound is normal, it is intentionally designed to help the user distinguish between power on and off. The image in the infrared night vision device is formed by a phosphor screen, and there is a little astigmatism, so it is not as clear as the image of the telescope used in the daytime. Tiny black specks may be seen in the image, this is a natural phenomenon formed during the manufacturing process of the reinforcement tube, not a quality issue.