If your trying to make a cecho during game play
what you need to do is make a script and then use this command.
Linedef 415.
http://wiki.srb2.org/wiki/Linedef_T...415/?s=2&_suid=110473218298103644260624052884
Theres also an example wad.
Your going to need a "Scriptname" and "Scriptislump"
You can find the command in "level header"
http://wiki.srb2.org/wiki/Level_Header#Level_Header/?s=2&_suid=110473291054708813474339963025
You won't find anything useful other then the script itself you must look in the actual map that triggers the script (linedef 415).
And for cechoduration is a console command for seconds. And "cechoflag" is another console command for a integer.
https://wiki.srb2.org/wiki/User:Monster_Iestyn/Console_Command_Categories
Got this from Monster Iestyn Wiki page.