Key ringer

[vimal333]

Hi,
I'm an engineering student .I'm trying to built a key ringer (which can be attached to the key as key chain so that it can be easily found out with the help of the beep sound when misplaced). I know its available in the market but wanted to make one of my own.i figured it out that it should have a RF transmitter receiver with a beeper attached tot he receiver ,but dunno really where to start.If u could give the necessary circuits that would be really helpful.