private static void LoudDialModem()
        {
            Console.WriteLine("LoudDialModem");
            Modem m = new HayesModem();
            Modem d = new LoudDialModem(m);

            Console.WriteLine((null == d.PhoneNumber));
            Console.WriteLine(0.Equals(d.SpeakerVolume));

            d.Dial("5551212");
            Console.WriteLine("5551212".Equals(d.PhoneNumber));
            Console.WriteLine(10.Equals(d.SpeakerVolume));
            Console.WriteLine("");
        }
        private static void CreateHayes()
        {
            Console.WriteLine("CreateHayes");
            Modem m = new HayesModem();

            Console.WriteLine((null == m.PhoneNumber));
            m.Dial("5551212");

            Console.WriteLine("5551212".Equals(m.PhoneNumber));
            Console.WriteLine(0.Equals(m.SpeakerVolume));

            m.SpeakerVolume = 10;
            Console.WriteLine(10.Equals(m.SpeakerVolume));
            Console.WriteLine("");
        }