In a custom device family, the config is captured using SSH based Perl Scripts, so the communication mode is defined in the script .
You should find the option to set the scripts below the Device Config Transfer Settings
For SSH you use one of the Perl Modules like " Net::SSH::Expect"
use strict;
use warnings;
use Net::SSH::Expect;
$ENV{'PATH'} = "/usr/bin:" . $ENV{'PATH'};
Take a look at the Perl Modules section in the below doc
Network Configuration Manager Extension Utility - CA Spectrum - 10.2 to 10.2.2 - CA Technologies Documentation
Below are some of the sample scripts which are already posted in communities, take a look at them and you will get some idea
Cisco IOS - SSH Capable Reload_Script (not Telnet!)
hp_procurve_capture_config.txt
Cisco WLC NCM Capture Script
NCM perl ssh des script for get Cisco ASA configuration