Serial Port /dev for apcupsd

[Barry Skidmore]

I am purchasing a APC Smart-UPS 420VA (with serial interface) for use
with apcupsd PORTVERSION=3.10.6 on a 5.1-RELEASE system, and have a
question about the correct /dev to specify in apcupsd.conf.  My machine
has one, standard serial port.

>From the Handbook, there appear to be two options, both of which exist
in /dev.

>From the Handbook:

      * Call-in ports are named /dev/ttydN where N is the port number,
        starting from zero. Generally, you use the call-in port for
        terminals. Call-in ports require that the serial line assert the
        data carrier detect (DCD) signal to work correctly.
        
      * Call-out ports are named /dev/cuaaN. You usually do not use the
        call-out port for terminals, just for modems. You may use the
        call-out port if the serial cable or the terminal does not
        support the carrier detect signal.

Which is the correct /dev to use in apcupsd.conf?

Thanks,
Barry