1.Previous
3.Next

alarm devices were often bells, drums, other musical instruments, or any items which made unusual loud noises that attracted the attention of the surrounding population.

Whistles were used by police in the 19th century. Steam whistles have been used on locomotives, ships, and in factories as alarm devices.

With the advent of electricity, a variety of other alerting devices have been invented, such as buzzers,

1.Previous
3.Next