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54 CHAPTER A: OPTIONAL CABLE SPECIFICATIONS
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 29 for details.
Table 29 Transmission Rate and Transmission Distance of V.24 (EIA/TIA-232)/V.35 Cable
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
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.
V.24 (EIA/TIA-232) DTE
Cable Pinouts
Figure 30 illustrates the V.24 DTE cable
V.24 (EIA/TIA-232) V.35
Baud Rate (bps)
Maximum
Transmission
Distance (m)
Baud Rate (bps)
Maximum
Transmission
Distance (m)
2400 60 2400 1250
4800 60 4800 625
9600 30 9600 312
19200 30 19200 156
38400 20 38400 78
64000 20 56000 60
115200 10 64000 50
- - 2048000 30
Type of
Equipment
Type of Interface Typical Equipment
DTE male PC or router
DCE female Modem, multiplexer or CSU/DSU