3Com NETBuilder SI Using Manual page 175

Serial Connectors and Flex-WAN Cables 175
DTEs include mainframes and automatic teller machines. DCEs include
modems and CSU/DSUs.
A DCE must always connect to a DTE, and vice versa. If you need to
connect a DTE to a DTE, or a DCE to a DCE, you can use a crossover cable
between the two devices.
For example, a SuperStack II bridge/router is a DTE. To connect the
bridge/router to another DTE, such as a mainframe, use a crossover
Flex-WAN DCE cable. The DCE cable has a DCE connector on the end
that connects to the mainframe (see Figure 29).
Figure 29 Connecting the Bridge/Router to a DTE Using a DCE Cable
Mainframe
SuperStack II
(acting DCE, provides
DTE
necessary clocking signals)
DTE
DCE
Connector
Flex-WAN DCE
crossover cable
To connect the bridge/router to a DCE, such as a modem, use a
straight-through Flex-WAN DTE cable. The DTE cable has a DTE connector
on the end that connects to the modem (see Figure 30).
Figure 30 Connecting the Bridge/Router to a DCE Using a DTE Cable
SuperStack II
DCE
DTE
DTE
connector
Modem
Flex-WAN DTE
straight-through cable