You can check if the modems or other ACUs are not working properly in several ways.
For more information, see Using Your Assigned Administrative Rights in Securing Users and Processes in Oracle Solaris 11.4.
# uustat -q
The line must be defined as direct in the /etc/uucp/Devices file. You must add a telephone number to the end of the command line if the line is connected to an autodialer or the device must be set up as direct. Type:
# cu -d -lline
line is /dev/cua/a.