Public Class Form1
    Private Delegate Sub DSub()
    Private PegelWechsel As New DSub(AddressOf Pinchange)
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        SerialPort1.RtsEnable = True
        SerialPort1.Open()
    End Sub
    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        SerialPort1.Close()
    End Sub
    Private Sub SerialPort1_PinChanged(ByVal sender As Object, ByVal e As _
      System.IO.Ports.SerialPinChangedEventArgs) Handles SerialPort1.PinChanged
        If e.EventType = IO.Ports.SerialPinChange.Ring Then Me.Invoke( _
        PegelWechsel)
    End Sub
    Private Sub Pinchange()
        Static z As Int32
        z += 1
        Label1.Text = z
        Console.Beep(1000, 50)
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        SerialPort1.RtsEnable = Not SerialPort1.RtsEnable
        SerialPort1.RtsEnable = Not SerialPort1.RtsEnable
    End Sub
End Class