Recently, new appliances have become built-in ethernet Port but most of the old devices have serial port. So, it complicates and needs long time to maintain at a long distance. It can only controllable and fixable using modem. In this paper, we developed an embedded STEP converter within Linux operating system and other application software so that serial devices(PBX) can control in the ethernet network After completion of development processes, test was conducted. In the remote places, it was connected the STEP converter and controled the serial PBX. Finally, we confirmed that it can apply to other equipments.