Public Class Form1
    Private Delegate Sub DS()
    Private STimer As New DS(AddressOf StartTimer)
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        SerialPort1.Open()
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        SerialPort1.DtrEnable = Not SerialPort1.DtrEnable            ' 
        ' PinChange auslösen
    End Sub
 
    Private Sub SerialPort1_PinChanged(ByVal sender As Object, ByVal e As _
      System.IO.Ports.SerialPinChangedEventArgs) Handles SerialPort1.PinChanged
        Me.Invoke(STimer)
    End Sub
 
    Sub StartTimer()
        Timer1.Start()
    End Sub
 
    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Timer1.Tick
        Console.Beep(1000, 50)
    End Sub
    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        SerialPort1.Close()
    End Sub
End Class