3Com Router 3012 Installation Manual page 54

54 C A: O
HAPTER PTIONAL
Synchronous and
Asynchronous mode
V.24 (EIA/TIA-232) DTE
Cable Pinouts
C S
ABLE PECIFICATIONS
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 29 for details.
Table 29 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 port 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 30 helps identify
DTE and DCE devices.
Table 30 Typical DTE and DCE
Type of
Equipment Type of Interface
DTE male
DCE female
In general, the asynchronous serial interface is connected to a modem or a
terminal adapter (TA) to act as the dial-up interface. In this case, it is unnecessary
to determine whether the device is DTE or DCE, you must only select the
appropriate baud rate.
Figure 30 illustrates the V.24 DTE cable
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
PC or router
Modem, multiplexer or CSU/DSU
Maximum
Transmission
Distance (m)
1250
625
312
156
78
60
50
30