Power and compatibility Operates from DC 5–12 V; recommended supply DC 9 V for optimal performance. External power supply is required (not included). When input voltage exceeds 7 V, the four central LEDs light. Built-in 3 V backup battery provides standby power; standby current is 2 mA when running on the backup battery. Working current is 35 mA when powered from an external supply. Clear, high-visibility time display Three two‑digit digital tubes show hours, minutes and seconds separately for immediate readability. Two small LEDs are used instead of a traditional colon to indicate time intervals. Bright, clear display ensures excellent visibility in typical indoor environments. Reliable, precise timing Uses AT89C2051 microcontroller for accurate and stable timekeeping. Low standby current extends backup battery life when external power is removed. Easy setup and calibration S1 button is dedicated to time calibration. Hold S1 for more than 2 seconds to enter calibration mode and set the time. Fast-touch adjustments let you change values quickly and precisely without complicated menus. Why you need this module Simple, ready-to-integrate time display for DIY electronics, repair, or retrofitting applications. Accurate timing and bright display make it suitable where a compact, visible clock is required. Low standby current and a 3 V backup battery preserve time settings during power interruptions. Typical use scenarios DIY electronics projects and hobbyist clock builds where a clear hours:minutes:seconds display is required. Educational and prototyping kits for teaching microcontroller-based timekeeping with a visible display. Retrofits or custom enclosures that need a precise, easy-to-calibrate digital clock module. What’s included / important notes Electronic clock kit (module) with three two‑digit digital tubes and control circuitry. Contains a 3 V backup battery for standby power. External DC power supply (5–12 V, recommended 9 V) must be provided separately. Technical summary Supply voltage: DC 5–12 V (recommended DC 9 V) Indicator behavior: four center LEDs on when supply > 7 V Backup battery: 3 V (for standby) Standby current (on backup): 2 mA Working current (external supply): 35 mA Controller: AT89C2051 Display: three two‑digit digital tubes (hours, minutes, seconds); two small LEDs for time intervals Calibration: S1 button, hold >2 s to enter calibration mode This module provides a precise, easy-to-use digital clock solution for DIY builds, repairs, and educational projects, with clear visibility, straightforward calibration, and reliable backup timing during power loss.