Some printers can print documents stored on memory cards or from digital cameras and scanners. Typical RGB input devices are color TV and video cameras, image scanners, and digital cameras. Windows 98 supports USB hubs, USB scanners and imaging class devices. Digital cameras can be used for the same purposes as dedicated scanners. Other input devices include webcams, microphones, joysticks, and image scanners. Travelers are screened by metal detectors and/or millimeter wave scanners. Sensors consisted of radar, sonar, infrared scanners, and radio. All modern ultrasound scanners use pulsed Doppler to measure velocity. Digital impressions can be made using dedicated optical scanners. Some new viruses, particularly ransomware, use polymorphic code to avoid detection by virus scanners. He also uses Bannertech to augment himself with devices including scanners and forcefields. Commercial laser scanners are in this subclass. This method usually gives better resolution than using attachments for digital A4 flat-bed scanners. Align Technology is a manufacturer of 3D digital scanners and clear aligners used in orthodontics. The best results are obtained using multidetector computed tomography (MDCT) scanners.