The Zebra QLN 420 Direct Thermal Mobile Printer with Apple iOS certification prints monochrome labels up to 4.1" wide at 203 dpi (8 dots/mm) for the retail, healthcare, and transportation industries. Wireless communication interface connection is 802.11 a/b/n dual radio with Bluetooth 3.0. It is Link-OS environment-enabled for integration, management, and maintenance from a PC, smartphone, or tablet with Apple iOS, Android, Windows Mobile, and BlackBerry systems. It has a 400 MHz 32-bit ARM processor with 128 MB RAM memory and 256 MB flash memory that supports downloadable programs, receipt formats, fonts, and graphics with 64 MB available for user storage. A plastic overmolding and tempered-glass display coupled with a seamless, one-piece design tolerates multiple drops from 6'/1.829 m to concrete and offers an IP43 dust- and water-resistance rating. A large, easy-to-read LCD control panel (240 x 128 pixels) can be customized using Wireless Markup Language (WML) text and icons and has five-way navigation buttons, two software-defined keys, printer alerts on the display, label odometer, a real-time clock, and help menus. The printer offers black-mark and gap media sensing using fixed center position sensors, a peel and present mode, a label present sensor for issuing labels one at a time, a tear bar for media dispensing, and center-loading media locking for variable roll widths. It prints both vertically and horizontally.