There are two ways to implement WaitForCall.

1st way:
   repeatedly call Online_ModemWaitForCall
See Modem1.frm

2nd way:
   Step1. Call Online_ATCmd to send "ATS=2" to the Modem.
          Here 2 means that the modem will automatically
          pick up the phone after 2 rings detected.

   Step2. Call Online_ModemEcho repeatedly until "CONTECT"
          or
          Call Online_ATCmd to send "ATS=0" to the Modem.
          Then the modem will not detect the "RING".
See Modem2.frm

The 1st is simply but not very efficent.

Remember that to some kind of modem, you have to send specific
initialization command to the modem. And the time delay for
the modem to response is diferent for different commands and
different modem. In these samples, it is supposed one second.
