Oscilloscope help

[kellyseye]

Commonly driven by a type 555 multi-function timer chip. Google '555 alarm schematic' and take your pick.
Also can be done using standard logic gates such as 2-NANDs in astable mode with another 2 providing the modulation therefore a single dual-input quad NAND package (4011 or 7400) will work. You can use NOR gates too.

[falingtrea]

You can also buy piezo devices that are already configured to output an alarm tone, aka piezo buzzers. Sonalert for one, comes to mind.