Complication · Striking & chiming
Alarm
Partially verifiedA mechanism that sounds an audible signal at a pre-set time, using a separate striking train and hammer independent of the main timekeeping train.
Definition
A mechanism that sounds an audible signal at a pre-set time, using a separate striking train and hammer independent of the main timekeeping train.
Historical origin
Mechanical alarm clocks date back centuries, with alarm pocket watches known from at least the eighteenth century; the mass-market mechanical alarm wristwatch is strongly associated with twentieth-century Swiss production, notably Jaeger-LeCoultre's Memovox line introduced in 1950.
How it works
A separate alarm barrel and train are wound independently of the going train (via a second mainspring or a shared but separately geared barrel), storing enough energy to drive a hammer against a bell, gong, or in wristwatches a vibrating disc or membrane for a set duration.
An alarm-setting disc beneath the dial, adjusted by the wearer via a separate crown or ring, carries a pin or cam that releases a locking lever when the hour hand (or a dedicated alarm-setting hand) reaches the chosen time, letting the alarm train run.
In wristwatch alarms such as the Memovox, the hammer strikes an internal resonance chamber or a dedicated membrane connected to the case back to project sound, since a full bell as used in alarm clocks or pocket watches is impractical at wristwatch scale.
Pocket watch context
Alarm pocket watches, sometimes called 'reveil' watches, used a small hammer and bell or gong housed within or behind the case, wound and set via a separate mechanism from the timekeeping train.
Wristwatch context
A specialist complication, most associated with mid-twentieth-century models like the Jaeger-LeCoultre Memovox, valued today partly for the mechanical ingenuity of producing an audible alarm in a wristwatch case.
Clock context
Alarm clocks are among the oldest and most common applications of the complication, using a bell struck by a separately wound train released at the set hour.
Identification
- A separate winding crown or a rotating inner bezel/disc for setting the alarm time, distinct from timekeeping winding and setting
- Visible or audible resonance chamber, gong, or bell depending on the object type
Servicing notes
The alarm train's separate mainspring and release mechanism should be assessed alongside, but distinctly from, the timekeeping train; complicated alarm watches and clocks should be serviced only by a specialist familiar with striking mechanisms.
General guidance only. Complicated mechanisms should be assessed and serviced by a qualified watchmaker or clockmaker specialist, not adjusted at home.
Related photographs
No confidently matched photograph of this subject has been found yet. These photographs show a closely related record, and are not examples of the type described on this page.
Sources & references
- Jaeger-LeCoultre company history regarding the 1950 Memovox, treated as a manufacturer claim
- de Carle, D., Watch and Clock Encyclopedia
Where sources disagree, the disagreement is stated rather than resolved silently.