Parallel and serial communications are two distinct ways of getting data from a PC to our printer. Serial communication transmits data on only 2 wires, one for sending and one for receiving one bit at a time. Parallel communication transmits data across multiple wires simultaneously. This provides a faster means of data transmission than serial. A parallel printer must be connected to a parallel port, commonly labeled as an LPT port on a PC. The LPT port should be set for bi-directional, standard, or SPP. A serial printer must be connected to a serial port, commonly labeled as a COM port on a PC. The COM port settings must match the printer serial settings to communicate properly. Please consult your PC�s literature to learn how to change these setting.