This simple circuit produces a loud trilling noise, if no valid transmitter signal is received.

Dimensions: 19 x 13 mm
Power Supply: 4 - 6 V (4 cells)

When you switch off the transmitter, the IC1, pin 5 provides a 2-KHz signal and pin 7 goes "high".

This frequency must correspond with the resonant frequency of the piezo element, otherwise the sound level will be very low.
Otherwise you should modify and compile the file "finder.asm":

.equ basis=69 ; timer für basis-frequenz

Increase or decrease the timer (standard value = 69).

If you use a buzzer with internal electronics producing the signal, R2 must be connected to pin 7 instead of pin 6.

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cover Book Description
How to make a high-quality display of any model aircraft. Teaches basic aircraft modeling preparation and assembly techniques. Includes suggestions for painting and decaling with special attention to creative displays and mounting tips for finished projects.