Avaya, Inc.
- 190 - PARTNER ACS 1600 DSL module User Guide
D. USI Cables
DTE or DCE?
A
Data Terminal Equipment
(DTE)
device transmits data on
the transmit pin and receives data on the receive pin, while a
Data Communication Equipment (DCE)
device transmits
data on the receive pin and receives data on the transmit pin.
Usually, the DCE device supplies the transmit clock timing for
both the DTE and DCE devices.
You must use a straight through cable to connect a DTE to a
DCE device. However, you must use a null modem cross
over cable to connect two DTE devices or two DCE devices.
For example, the serial port on a PC is a DTE device, while
most modems are DCE devices. To connect a PC to a
modem, you use a straight through cable. To connect two
PCs together, you use a null modem cross over cable.
Which
Hardware
Protocol?
You can configure the USI port on the PARTNER ACS 1600
DSL module for V.35 or RS-530. Each of these hardware
interfaces uses different voltage levels, so they are not
compatible electrically.
However, there are other hardware interface standards that
use the same voltage levels, but with different connectors:
RS-449 and V.36 are the same electrical interface as
RS-530.
The DB25 connector, which must be shielded, is wired for RS-
530, which is a superset of all the other hardware interfaces.
Only RS-530 uses DB25 connectors - the other hardware
interfaces use different types of connectors.
