One of my readers is always concerned about the availability of some components used in my circuits. Even though new makes are releasing continuously, the old makes are still in the market. Indian electronics market is rich in new as well as old components and the old one cannot be considered as obsolete. Substitutes are also easily available. We cannot argue if the component is not available in one country since the availability and use varies in different regions. A wise designer can easily substitute a component if the make shown in the circuit is not available.
If you feel threatened or need an urgent support in a crowd, use this alarm to catch the attention of others. It generates a loud siren simulating that of the Fire brigade which is enough to get support from others. A single press on the switch can activate the siren for 2 minutes and then it automatically stops. It is too small enough to keep in the pocket or hand bag.