Serial Ports

The serial port, also known as RS-232 or COM (communication) ports (see Figure 8.4), historically has rivaled the parallel port in versatility. Serial ports have been used to connect

  • External modems

  • Serial mouse or pointing devices such as trackballs or touchpads

  • Plotters

  • Label printers

  • Serial printers

  • File transfer programs such as Direct Cable Connection, LapLink, and Interlink

Figure 8.4. A 9-pin serial port (DB-9M connector, top) and a 25-pin serial port (DB-25M connector, bottom) on a typical extension bracket from an ISA multi-I/O card. The ribbon cables used to connect the ports to the card can be seen in the background.

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