Dell Precision 420 - Manual (Page 69)

I/O Ports and Connectors
The I/O ports and connectors on the back panel of your computer are the gateways through which your computer system communicates with
external devices, such as a keyboard, mouse, printer, and monitor.
Figure 3 identifies the I/O ports and connectors for your computer.
Figure 3. I/O Ports and Connectors
Serial and Parallel Ports Overview
The two built-in serial ports use 9-pin D-subminiature connectors on the back panel. These ports support devices such as external modems,
printers, plotters, and mice that require serial data transmission (the transmission of data one bit at a time over one line).
Most software uses the term COM (for COMmunications) plus a number to designate a serial port (for example, COM1 or COM2). The default
designations of your computer's integrated serial ports are COM1 and COM2.
The integrated parallel port uses a 25-pin D-subminiature connector on the computer's back panel. This I/O port sends data in parallel format
(where eight data bits, or one byte, are sent simultaneously over eight separate lines in a single cable). The parallel port is used primarily for
printers.
Most software uses the term LPT (for Line PrinTer) plus a number to designate a parallel port (for example, LPT1). The default designation of your
computer's built-in parallel port is LPT1.
MOUSE PS/2 mouse connector
NIC 10/100 Ethernet RJ45 connector
PANEL Control panel connector
PARALLEL/SCSI Parallel connector over Wide SCSI connector (stacked)
PCI1, PCI2, PCI3 PCI expansion-card connectors on primary PCI bus
PCI4, (PCI5) PCI expansion-card connectors on secondary PCI bus
PCI5\RAIDPORT RAID port connector extension to PCI5
RAID Optional RAID PCI expansion card connector extension
SCSI_LVD Primary (LVD/Wide) SCSI connector
SCSI_NARROW Secondary (Narrow) SCSI connector
SERIAL1/2 Serial port connectors (sometimes referred to as
COM1 and COM2; stacked)
SPKR Internal speaker connector (on control panel)
TAPI Telophony microphone and speaker connector
PROC_0 SECC2 cartridge connector for processor 0
PROC_1 SECC2 cartridge connector for processor 1
USB 1/2 USB connectors (stacked)
WUOL Remote wakeup on LAN connector
NOTE: For the full name of an abbreviation or acronym used in this table, see the Glossary .
1 Parallel port connector
2 Serial port 1 connector
3 PS/2 mouse connector
4 PS/2 keyboard connector
5 USB connectors
6 Video out connector (may be
in bottom or second
expansion slot)
7 NIC connector
8 Diagnostic LEDs
9 Line-in jack
10 Line-out jack
11 Microphone jack
12 Serial port 2 connector
13 External SCSI connector