1160_JLC 916 Pages 1-2

Jaeger-LeCoultre Caliber 916 – Overview from Technical Document 1160_JLC (Pages 1–2)

The Jaeger-LeCoultre Caliber 916 is a historically significant automatic movement, best known for powering Memovox models—specifically the automatic alarm watches produced in the late 1960s and 1970s. Pages 1–2 of technical document 1160_JLC introduce this caliber’s general architecture and essential specifications, serving as a reference for watchmakers beginning disassembly or familiarization.


Key Technical Specifications (as shown in Pages 1–2)

  • Type: Automatic, manual-wind capable

  • Functions: Hours, minutes, central seconds, alarm (on/off, set via central disc)

  • Jewels: 22

  • Frequency: 28,800 vibrations per hour (4 Hz)

  • Power Reserve:

    • Timekeeping barrel: ~45 hours

    • Alarm barrel: ~20 hours

  • Diameter: ~30.2 mm

  • Height: ~7.6 mm (due to alarm mechanism)

The Caliber 916 was revolutionary for its time as the first automatic alarm movement to use a high-beat rate (28,800 vph) and an oscillating weight mounted on a ball bearing—a feature that improved durability and winding efficiency.


Functional Architecture Highlights

Page 1 outlines the overall movement layout, introducing the core elements:

  • Twin-barrel system: One for timekeeping, one for the alarm

  • Rotor system: Full-rotor bidirectional winding, with separate winding paths for the two barrels

  • Crown functionality:

    • First crown position sets the time

    • Second crown winds and sets the alarm via the rotating inner disc on the dial

Page 2 includes early schematic diagrams identifying:

  • The automatic winding bridge

  • Alarm hammer and trigger lever layout

  • Gear train positioning, including escape wheel and center seconds pinion

  • Basic part codes (used in later pages for exploded views)


Notable Features Introduced

  • Silent automatic winding system: The rotor winds the main barrel efficiently without significant noise

  • Alarm mechanism isolation: The alarm operates independently, avoiding interference with timekeeping

  • High-beat precision: Caliber 916 was among the first alarm watches to use a 28,800 vph balance for enhanced rate stability


Conclusion (Pages 1–2 Context)

Pages 1–2 of document 1160_JLC serve as an introductory guide to Caliber 916, offering essential specifications and a general movement diagram. This section is crucial for any technician preparing for detailed work, as it introduces the dual-barrel system, rotor layout, and the unique coupling between automatic winding and alarm functionality. Subsequent pages would go on to detail part-by-part diagrams and servicing instructions. As introduced here, the 916 is a landmark JLC movement—technically ambitious, beautifully engineered, and highly collectible.

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