Install dahdi-firmware-nonfree by entering the following commands in the terminal:
sudo apt update sudo apt install dahdi-firmware-nonfree
Description:
DAHDI non-free firmware
DAHDI (formely Zaptel) is an interface for telephony devices used by e.g. the Asterisk PBX software. The dahdi-* packages provide the DAHDI kernel modules and their required setup environment. . This package includes the non-free firmwares from the DAHDI tarball as well as downloading script for the Digium firmwares that are normally downloaded on 'make install'.
Homepage: http://www.asterisk.org/
Version: 2.11.1.0.20170917-1
Section: multiverse/comm