During this period of 20 years, Mr Hudson devoted himself to studying the types of Sai Ren and produced many special Sai Ren. Scotland Yard is a big user, and some other farmers in Britain also use alarms as alarms or warnings in fields or manors.
Sirens have replaced the traditional knocking warning communication tools that have been used for thousands of years. Its only advantage is that you can bite the edge of your mouth with your teeth or lips, and you don't need to hold it with your hands to make a warning sound. The invention of the alarm obviously liberated the hands of the "metropolitan" police who used these devices.
When this siren blows, it can be heard within two miles. On March 22, 1884, the police opened a special telephone line to inform the public of all kinds of alarm sounds, so that the general public can be fully familiar with the sounds of all kinds of alarm sounds.
1898, Mr Hudson further improved the alarm, and J Hudson Company applied for a patent to strengthen their "monopoly" position in the British market. At this time, imitators or competitors appeared all over the country. "City" sirens are still produced in Britain today and provided to police forces. Although the manufacturing methods are more advanced and the styles are more diverse, the essence of the basic products is still the same as many years ago.