The locating beeper that I have used is the Beeper from programming by Pete for this however I have used Surface mount components and etched a circuit board. This makes the whole circuit including battery and holder very compact indeed. All components can be purchased from Maplins including a PCB etching kit, part numbers shown below are for Maplins, the total cost of the beeper including battery is less than £5.00. Calculations show the battery should last for 60 hours continuous use.

schem.gif (4294 bytes)

Click to enlarge