dial_tone: 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/dial_tone - from package: gnuradio

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

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