Horologists seem to prefer this Shakespearean spelling for a clock or watch that sounds a warning bell at a pre-set time.
Alarum mechanisms are found on some of the earliest mechanical timekeepers and were being fitted to watches before 1600
The verge escapement remain the only form of escapement generally used in all clocks and watches until about 1670, nearly four centuries after its successful, but as yet anonymous, application to the problem of time-measurement. The verge escapement consists of three parts, which can most clearly been seen and understood in the large "turret" clock from Cassiobury Park, which, like the Dover Castle clock (now in the Science Museum, London), was formerly thought to have been made in the fourteenth century. Both are now regarded as probably no older than the sixteenth century. Nevertheless, the method of construction of this clock, with its massive heavy wrought-iron frame and mechanism, is in the medieval tradition and scarcely differs from the oldest surviving clock in Britain – the Salisbury Cathedral clock of 1386
Flieger Automatic 595.10.46 ...
Relojes Alarum: Precios Relojes diccionario, Relojeria Alarum