&C1      &C0 = means the modem should lie to the computer and
          pretend the other modem is alive and well even when it
          is not.  NEVER USE &C0.
          &C1 = means the DCD Data Carrier detect line from the
          modem to the computer should function normally so the
          computer can tell if the remote modem is still present
          or if it has hung up.  ALWAYS USE &C1.