design_coupler: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/design_coupler - from package: atlc

You may install the required package with command apt-get install {package}
Error in other languages:
design_coupler: bevel nie gevind nie
design_coupler: comandă negăsită
design_coupler: comando não encontrado
design_coupler: commande introuvable
design_coupler: command not found
design_coupler: käsku ei ole
design_coupler: không tìm thấy lệnh
design_coupler: komanda nerasta
design_coupler: Kommando nicht gefunden.
design_coupler: kommandot finns inte
design_coupler: komut yok
design_coupler: nie znaleziono polecenia
design_coupler: níor aimsíodh an t-ordú
design_coupler: no se encontró la orden
design_coupler: no s'ha trobat l'ordre
design_coupler: opdracht niet gevonden
design_coupler: parancs nem található
design_coupler: perintah tidak ditemukan
design_coupler: príkaz nenájdený
design_coupler: příkaz nenalezen
design_coupler: команда не найдена
design_coupler: командата не е открита
design_coupler: 命令找不到
design_coupler: コマンドが見つかりません