What is the difference between DTE & DCE???
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Answer Posted / ashish kumar tiwari
Most data communication protocols specify communications
between two types
of equipment. Typically, one is called DTE (Data Terminal
Equipment) and the
other is called DCE (Data Circuit-Terminating Equipment).
For instance, in EIA-
232 communications, DTE devices (terminals, PCs, mini-
computers) are quite
stubborn and only want to talk to DCE devices (modems,
multiplexers), and vice
versa. For this reason, you may connect a PC COM port to a
modem using a
"straight through" EIA-232 cable. However, when you must
connect a PC COM
port to another PC COM port, you must use a "null-modem"
cable. The function
of the null modem cable is to "trick" the DTE device into
believing that it is
talking to a DCE device by cross-wiring the data and
control pins in the cable.
Ethernet AUI (Attachment Unit Interface) also uses the
DTE/DCE convention,
However, itÕs not as simple as it is with EIA-232.
The AUI port of a WorkstationÕs NIC (Network Interface
Card) is a female DB-15
DTE. So is the AUI port on a multiport hub/repeater such as
PattonÕs Model
2108. The AUI port of an Transceiver like the Model 2100,
is a male DB-15
configured DCE. Therefore, it can plug directly into AUI
port of the NIC or to the
Model 2108.
The problem comes with the need to connect a DTE to another
DTE, or a DCE to
another DCE. The answer is simple: Unlike RS-232, it canÕt
be done with just a
cable.
If it were simply a matter of crossing the DI (Data In)
pins to the DO (Data Out)
pins via a null modem cable, the matter could be solved
simply. However, the CI
(Control In) signals are used specifically by the DCE to
indicate to the DTE that a
collision has been detected or during a Signal Quality
Error. If one were to
connect a DTE device to another DTE device with a null
modem cable, there
would be no provision for this signal. Similarly,
connection between two DCEs
would cause these signals to conflict with one another.
There are CO (Control
Out) signals in Ethernet, but these signals are used for
another function and are
almost never used. So whatÕs the solution when connecting
two DTEs together?
In order to connect two DTEs together, such as a
workstation to a Model 2108
hub, two Model 2100s may be used, one connects to the
workstationÕs AUI port,
and the other to the AUI port of the Model 2108 with 10Base-
T twisted pair
connections in between. The Model 2108 also allows up to 8
additional 10Base-T
connections at UTP connections up to 330 ft
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