3Com Router 3016 Installation Manual page 28

28 C 3: I
HAPTER NSTALLING THE
Connecting the
Synchronous/
Asynchronous Serial
Interface to a CSU/DSU
R
OUTER
To connect the AUX cable:
1 Turn off power to the router.
2 Plug the RJ-45 connector of the AUX cable into the AUX port of the router.
3 Connect the DB-25 or DB-9 adapter of the AUX cable to the serial interface of the
analog modem.
For pinout details of the AUX cable, see Appendix A.
The synchronous/asynchronous serial interface is usually used to connect a WAN
device, such as a modem, and a CSU/DSU. It can operate in
synchronous/asynchronous mode and DTE/DCE mode. For the attributes of the
interface, see Chapter 1, Overview.
Synchronous and Asynchronous mode
V.35 and V.24 (EIA/TIA-232) standards support synchronous operating mode,
while only V.24 (EIA/TIA-232) standard supports the asynchronous operating
mode. The maximum transmission distance and baud rate of the signal vary with
the operating mode. See Table 1 for the details.
Table 1 Transmission Rate and Transmission Distance of V.24 (EIA/TIA-232)/V.35 Cable
V.24 (EIA/TIA-232)
Baud Rate (bps)
2400
4800
9600
19200
38400
64000
115200
-
Caution: The baud rate should not exceed 64 Kbps when the V.24 cable operates
in synchronous mode.
DTE and DCE mode
The synchronous serial interface can operate in both DTE mode and DCE mode.
For two devices connected directly, one device should operate in DTE mode, and
the other device should operate in DCE mode. The DCE mode device provides a
synchronous clock and specifies the transmission rate, the DTE mode device
accepts the synchronous clock and communicates at the specified transmission
rate. Usually, the router serves as the DTE device. To determine whether the device
is a DTE or a DCE, refer to the user manual for the device. Table 2 helps identify
DTE and DCE devices.
Typical DTE and DCE
Table 2
Type of
Equipment Type of Interface
V.35
Maximum
Transmission
Distance (m) Baud Rate (bps)
60 2400
60 4800
30 9600
30 19200
20 38400
20 56000
10 64000
- 2048000
Typical Equipment
Maximum
Transmission
Distance (m)
1250
625
312
156
78
60
50
30