Bulle Electric Clocks

Movement & mechanism

• A free pendulum carrying a small permanent magnet swings past a fixed coil, which both detects the pendulum's passage and, periodically, receives a battery-powered impulse to sustain the swing
• No mainspring, weight, or conventional escapement train is present; the pendulum itself is both the timekeeping element and, effectively, its own self-contained oscillator
• Hands are advanced from the pendulum's motion via a simple ratchet or similar mechanical counting arrangement
• Power drawn from a single dry or wet-cell battery, intended to run for an extended period, commonly cited by the maker as up to about a year, between replacements

Identification

• Absence of any visible mainspring winding arrangement or driving weight is a strong indicator of this or a related electrically impulsed clock type
• A coil and magnet assembly mounted near the base of the pendulum, rather than an anchor and escape wheel, distinguishes the mechanism internally
• Maker's name or 'Bulle' branding on the dial or movement supports specific attribution

Terminology

• Free pendulum — a pendulum that swings largely unconstrained by mechanical escapement, receiving only periodic electromagnetic impulses
• Master–slave clock — a related but functionally distinct system in which a single master clock periodically synchronises multiple simple slave dials, rather than each clock sustaining its own pendulum electrically

Known variations

• Mantel-cased Bulle clocks
• Longcase-format Bulle clocks
• Related, but mechanically distinct, early battery-driven pendulum clocks by other continental makers

Collecting notes

Bulle and comparable early battery-driven pendulum clocks are collected as a distinct step in the history of electrical timekeeping; because the coil, magnet and battery-contact assembly are specific to the type and can be lost or replaced, mechanical and electrical originality is a significant conservation consideration.