dp: command not found

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

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

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/dp - from package: speech-tools

You may install the required package with command apt-get install {package}

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