3Com 3C13701 Installation Guide - Page 31

Connecting Router to the WAN 31 Connecting WAN Interface to DSU/CSU Connecting Synchronous/Asynchronous Serial Interface to DSU/CSU Introduction to the Synchronous/Asynchronous Serial Interface. The fixed WAN interface of 3Com 5000 Routers is a synchronous/asynchronous serial interface, which is usually used for the connection with a WAN device, such as a Modem or CSU/DSU. It can operate in the synchronous/asynchronous mode or DTE/DCE mode, depending on the application. For the attributes of the interface, please refer to Table 16. Table 16 Attributes of the synchronous/asynchronous serial interface Attribute Connector type Interface standard and operating mode Minimum baud rate (bps) Maximum baud rate (bps) Matching cable Function Protocol Description Synchronous DB28 or DB50 Asynchronous V.24 V.35/X.21 RS232 DTE/DCE DTE/DCE 1200 1200 300 64K 2.048M 115200 V.24 (RS232) DTE cable V.24 (RS232) DCE cable V.35 DTE cable V.35 DCE cable X.21 DTE cable X.21 DCE cable DDN leased line backup Terminal access Modem dial-up Backup Asynchronous lease line terminal access PPP PPP MP SLIP LAPB MP HDLC X.25 Frame Relay ■ Synchronous/asynchronous mode Synchronous/Asynchronous serial interface can work in either synchronous or asynchronous mode. Different signaling standards are supported in these two modes. V.35 and V.24 (RS232) support synchronous operating mode, while V.24 (RS232), support the asynchronous operating mode. The maximum transmission distance and baud rate of the signal vary with the operating mode.