I found this "hidden" courtesy in app_rpt.c:
{"ranger","|t(1800,0,60,3072)(0,0,50,0)(1800,0,60,3072)(0,0,50,0)(1800,0,60,3072)(0,0,50,0)(1800,0,60,3072)(0,0,50,0)(1800,0,60,3072)(0,0,50,0)(1800,0,60,3072)(0,0,150,0)"}
This one is not (re-)defined in my default rpt.conf.
According to the source, this "ranger" courtesy is sent when a "RANGER" node is connected. Also, all "RANGER" node numbers should begin with "9". And my Echolink node number, choosed at random, is... 99 !
So, I found my answer 
But, what on earth is a "RANGER" node ???
···
Le 14/04/2016 12:06, Toussaint OTTAVI a écrit :
I was wondering if there are some hidden and/or hardcoded CTs. I'll try browse the sourcecode ASAP.
--
Then, I'll try to :
- rename my Echolink node number to something else not starting with "9"
- redefine the "ranger" ct in rpt.conf. That would allow a "special" ct when the Echolink node is connected (which is an interesting behavior)