来电显示的实现
MODEM的AT命令CID和VCID是设置是不是来电显示的，如果电信开通了来电显示功能
就能通过MODEM来显示对方的电话号码。那么首先设置CID=1或是VCID=1

般来说来电显示的信息为：
DATE = MMDD "来电日期 MMDD
TIME = HHMM "来电时间 HHMM
NMBR = ######## "来电号码
程序实现如下,设置MSComm1的相关设置，并建两个Label为Label1和Label2
Function OpenCID(OpenCLose As Boolean) As Boolean
'打开或是关毕来电显示功能
    On Error Resume Next
    Dim ArrCID(1) As String
    ArrCID(0) = "at#cid=" & IIf(openclode, 1, 0)
    ArrCID(1) = "at#vcid=" & IIf(openclode, 1, 0)
    MSComm1.RThreshold = 0
    For i = 0 To 1
        MSComm1.Output = ArrCID(i) & vbCr
        EndTime = Timer + 0.5
        Do While bStop = False
            nTemp = nTemp + 1
            If MSComm1.InBufferCount >= 2 Then
                sTemp = MSComm1.Input
                If InStr(sTemp, "OK") = 0 Then
                    bStop = True
                    OpenCID = True
                    Exit Function
                End If
            End If
            If Timer >= EndTime Or ErrorCode Then Exit Do
        Loop
    Next i
    OpenCID = False
    MSComm1.RThreshold = 1
End Function
下面的函数显示来电号码并在窗体上的Label1的Label2上显示出来
Private Sub MSComm1_OnComm()
    On Error Resume Next
    Static Buffer As String
     ' 收到多于 RThreshold 属性设置的字符数（RThreshold 属性必须大于 0）。
            'label1 = "收到" + Str(MSComm1.InBufferCount) + "个字符"
            Buffer = Buffer + MSComm1.Input
            Buffer = UCase(Buffer)

         '   Exit Sub
            If InStr(1, Buffer, "RING", vbTextCompare) Then
            '收到震铃
                'Comm1.Output = "ATA" + Chr(13) '命令 Modem 摘机响应
                Buffer = "" '清缓冲区字符
                'mciExecute "sound " & SystemPath & "\ringin.wav"
                Label1 = "状态：收到震铃"
                Zhen = True
                frmCallID.Show
                frmCallID.ChangRing
             
               
            ElseIf InStr(1, Buffer, "CONNECT", vbTextCompare) Then
            '对方应答呼叫
                Buffer = "" '清缓冲区字符
                Label1 = "状态：已经建立连接"
            ElseIf InStr(1, Buffer, "BUSY", vbTextCompare) Then
            '对方线路忙
                Buffer = "" '清缓冲区字符
                Label1 = "状态：对方线路忙"
            ElseIf InStr(1, Buffer, "No DIA", vbTextCompare) Then
                Buffer = "" '清缓冲区字符
                Label1 = "状态：拨出号码错,请检查电话线"
                Command1_Click
            ElseIf InStr(1, Buffer, "No CARRIER", vbTextCompare) Then
            '对方未摘机或未响应
                Buffer = "" '清缓冲区字符
                Label1 = "状态：对方未摘机"
          
            ElseIf InStr(1, Buffer, "NMBR =", vbTextCompare) Then
             tmpStr = InStr(1, Buffer, "NMBR", vbTextCompare)
             CallNum = Right(Buffer, Len(Buffer) - lll - 6)
             Label2.Caption = "对方电话：" + CallNum

                'Buffer = "" '清缓冲区字符
            ElseIf InStr(1, Buffer, "OK", vbTextCompare) And Asc(Right(Buffer, 1)) = 10 Then
              If Zhen = False Then Buffer = "" '清缓冲区字符
             If Command1.Caption = "挂断" Then
              Label2.Caption = "状态：已经播通电话：" + txtCallNum
            End If
            End If
End Sub