Cisco WS-C1912-A Hardware Installation Guide - Page 47

Chapter 3 Cable Information and Specifications for Cisco 1900 Series Routers Preparing to Connect to a Network the shielded serial transition cable has a DB-60 connector, which connects to the DB-60 port on a serial WIC. The other end of the serial transition cable is available with a connector appropriate for the standard that you specify. The synchronous serial port can be configured as DTE or DCE, depending on the attached cable (except EIA-530, which is DTE only). To order a shielded cable, contact customer service. See the "Obtaining Documentation and Submitting a Service Request" section on page xvi. Note All serial ports configured as DTE require external clocking from a channel service unit/data service unit (CSU/DSU) or other DCE device. Although we do not recommend manufacturing your own serial cables (because of the small size of the pins on the DB-60 serial connector), cable pinouts are provided in the Cisco Modular Access Router Cable Specifications. Transmission Speeds and Distance Limitations Serial signals can travel a limited distance at any given bit rate; generally, the slower the data rate, the greater the distance. All serial signals are subject to distance limits, beyond which a signal is significantly degraded or is completely lost. Table 3-2 lists the recommended maximum speeds and distances for each serial interface type; however, you might get good results at speeds and distances greater than those listed, if you understand the electrical problems that might arise and can compensate for them. For instance, the recommended maximum rate for V.35 is 2 Mbps, but 4 Mbps is commonly used. Table 3-2 Serial Signal Transmission Speeds and Distances Rate (bps) 2400 4800 9600 19200 38400 56000 1544000 (T1) Distance for EIA/TIA-232 Feet Meters 200 60 100 30 50 15 25 7.6 12 3.7 8.6 2.6 - - Distance for EIA/TIA-449, X.21, V.35, and EIA-530 Feet Meters 4100 1250 2050 625 1025 312 513 156 256 78 102 31 50 15 Distance for USB Feet Meters 16.4 5 16.4 5 16.4 5 16.4 5 16.4 5 16.4 5 16.4 5 Balanced drivers allow EIA/TIA-449 signals to travel greater distances than EIA/TIA-232 signals. Typically, EIA/TIA-449 and EIA-530 can support a 2-Mbps rate, and V.35 can support a 4-Mbps rate. Asynchronous/Synchronous Serial Module Baud Rates The following baud-rate limitations apply to the slow-speed serial interfaces in the asynchronous/synchronous serial modules: • Asynchronous interface-Maximum baud rate is 115.2 kbps. OL-19084-01 Cisco 1900 Series Hardware Installation 3-5