brltty-ttb: 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/brltty-ttb - from package: brltty

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

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