Atomic projection alarm clock alternates both time and/or outdoor temp (F/C) on your ceiling or wall with arm rotation for proper viewing and auto-focus. Easy to read numbers. Wireless temp sensor transmits within seconds to the clock. Clock receives accurate atomic time for updates and will reset for daylight saving time. Perpetual calendar and time zone setting. Displays indoor temp and date, and has LED backlight and time alarm with snooze. Outside temperature range: -39.8 F to 139.8 F. Inside temperature range: 14 F to 99.9 F. Projection alarm: 3 AA alkaline batteries (not included) or AC power adapter (included). Sensor: 2 AA alkaline batteries (not included).