This project has been designed to interface an EIA-232 channel to an EIA-485 half-duplex bus. We should do so because EIA-485 offers more features than 232, especially where we apply a long distance wired communication involving more than two devices.The EIA-232 standard, formerly known as RS-232, was introduced about thirty years ago, well before the first application of desktop sized personal computers. The RS-232 standard mainly covers the communication between DTEs and DCEs, where DTEs are Data Circuit Terminating Equipments, and DCEs are Data Communication Equipments. A typical DTE could be just a video terminal, a printer, or even a personal computer — it can operate either as a source or destination of data, hence it is the equipment where the communication is terminated.