3Com MSR 20, MSR 30, MSR 50 DTE and DCE, Interface attributes of the FIC-2SAE/FIC-4SAE/FIC-8SAE

154CHAPTER 4: FLEXIBLE INTERFACE CARDS

DTE and DCE

An FIC-SA card is usually connected to an external modem for dialing purpose, where an appropriate baud rate setting is required.

The synchronous serial interface can work in either DTE or DCE mode. Two directly connected devices must work as DTE and DCE respectively. The DCE provides clock synchronization and specifies the communication rate, whereas the DTE accepts clock synchronization and communicates at the specified rate.

The router normally works as a DTE. To identify whether the equipment connected to the router is DTE or DCE, refer to the manual shipped with the equipment.

Speed and transmission segment of synchronous/asynchronous serial interface

In different operating modes, the synchronous/asynchronous serial interface supports different electric signal specifications and baud rates. In addition, the maximum signal transmission segment depends not only on the specified baud rate but also on the selected cable. The following table shows how the cable type, baud rate, and the maximum signal transmission segment related to each other.

Table 108 Speed and transmission segment of the V.24 (RS232)/V.35 cable

V.24 (RS232)		V.35
	Max. transmission		Max. transmission
Baud rate (bps)	segment	Baud rate (bps)	segment
2400	60 m (196.9 ft.)	2400	1250	(4101 ft.)
4800	60 m (196.9 ft.)	4800	625 m (2050.5 ft.)
9600	30 m (98.4 ft.)	9600	312 m (1023.6 ft.)
19200	30 m (98.4 ft.)	19200	156 m (511.8 ft.)
38400	20 m 65.6 ft.)	38400	78 m (255.9 ft.)
64000	20 m (65.6 ft.)	56000	60 m (196.9 ft.)
115200	10 m (32.8 ft.)	64000	50 m (164 ft.)
-	-	2048000	30 m (98.4 ft.)

n When a V.24 cable is used, the baud rate of the FIC-SA in synchronous mode shall not exceed 64 Kbps.

Interface Attributes The following table describes the interface attributes of the FIC-SAE:

Table 109 Interface attributes of the FIC-2SAE/FIC-4SAE/FIC-8SAE

	Description
Attribute	Synchronous	Asynchronous
Connector	DB-28
Number of connectors	2 (FIC-2SAE)
	4 (FIC-4SAE)
	8 (FIC-8SAE)