Hello, Iam yashwanth agrawal. Studying my b.tech second year. i want to do a project on secret bell. So i need to know the circuit diagram of it and a clear description of how thee circuit works and the wa it can be used in real time application.I currently am aware of what exactly is secret bell about and i have no idea of which digital ic to be used and all. I need to know from the root of it. So i hope that i will be answered for my questions very soon. And i will be very thankful if you can suggest me some intersting mini project, but the basic constraint is i can use only 74 series in digital ic's.

try this.
make suitable changes in resistor,capacitor values according to give.
post me some another circuit of this type if u hav.

to get information about the topic secret bell full report ppt and related topic refer the page link bellow
http://seminarsprojects.in/attachment.php?aid=15809

http://studentbank.in/report-secret-bell--26177

http://studentbank.in/report-secret-bell