Oscilloscope help

[Darrel Taylor]

FREQOUT makes sine waves and must be filtered, which is not what you need.
Try this ...

PiezoPIN  VAR PORTC.2
TMR0IF    VAR INTCON.2
Width     VAR BYTE
OPTION_REG = %11010011 ; TMR0 1:16

Alarm:
    FOR Width = 161 TO 120 STEP -1
        WHILE !TMR0IF
            TOGGLE PiezoPIN
            PAUSEUS Width
            TOGGLE PiezoPIN
            PAUSEUS Width
        WEND
        TMR0IF = 0
    NEXT Width
GOTO Alarm

[Megahertz]

Thanks Darrel and everyone. It's done

[Megahertz]

Just out of curiosity, can this be achieved without using a microcontroller?

[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.