root@srv-lx-fs-01:~# lsb_release -d

Description: Debian GNU/Linux 9.8 (stretch)

root@srv-lx-fs-01:~# wget -O - https://files.freeswitch.org/repo/deb/freeswitch-1.8/fsstretch-archive-keyring.asc | apt-key add -

--2019-04-09 00:58:39--  https://files.freeswitch.org/repo/deb/freeswitch-1.8/fsstretch-archive-keyring.asc

Connecting to 10.88.7.3:3128... connected.

GnuTLS: A TLS warning alert has been received.

GnuTLS: received alert [112]: The server name sent was not recognized

Proxy request sent, awaiting response... 200 OK

Length: 3155 (3.1K) [text/plain]

Saving to: ‘STDOUT’

-                                       100%[==============================================================================>]   3.08K  --.-KB/s    in 0s

2019-04-09 00:58:39 (23.6 MB/s) - written to stdout [3155/3155]

OK

root@srv-lx-fs-01:~# echo "deb http://files.freeswitch.org/repo/deb/freeswitch-1.8/ stretch main" > /etc/apt/sources.list.d/freeswitch.list

root@srv-lx-fs-01:~# echo "deb-src http://files.freeswitch.org/repo/deb/freeswitch-1.8/ stretch main" >> /etc/apt/sources.list.d/freeswitch.list

root@srv-lx-fs-01:~# cat /etc/apt/sources.list.d/freeswitch.list

deb http://files.freeswitch.org/repo/deb/freeswitch-1.8/ stretch main

deb-src http://files.freeswitch.org/repo/deb/freeswitch-1.8/ stretch main

root@srv-lx-fs-01:~# apt-get update

Hit:1 http://files.freeswitch.org/repo/deb/freeswitch-1.8 stretch InRelease

Ign:2 http://ftp.us.debian.org/debian stretch InRelease

Hit:3 http://ftp.us.debian.org/debian stretch-updates InRelease

Hit:4 http://ftp.us.debian.org/debian stretch Release

Hit:6 http://security-cdn.debian.org/debian-security stretch/updates InRelease

Reading package lists... Done

So, so far everything looks good, but my problem is with the following command:

root@srv-lx-fs-01:~# apt-get build-dep freeswitch

Reading package lists... Done

Reading package lists... Done

Building dependency tree

Reading state information... Done

Some packages could not be installed. This may mean that you have

requested an impossible situation or if you are using the unstable

distribution that some required packages have not yet been created

or been moved out of Incoming.

The following information may help to resolve the situation:

The following packages have unmet dependencies:

 builddeps:freeswitch : Depends: libks but it is not installable

                        Depends: signalwire-client-c but it is not installable

                        Depends: libv8-6.1-dev but it is not installable

E: Unable to correct problems, you have held broken packages.

Any ideas please?