Cisco 3825 Hardware Installation Guide - Page 105

Chapter 5 Connecting Serial Network Modules About Serial Connections All serial interface types except EIA/TIA-530 and EIA/TIA-530A are available in DTE or DCE format: DTE with a plug connector at the network end, and DCE with a receptacle at the network end. V.35 is available in either mode, with either gender at the network end. EIA/TIA-530 and EIA/TIA-530A are available in DTE only. Serial cables are not provided with the network module. For ordering information, see the "Obtaining Technical Assistance" section on page xi. Although manufacturing your own serial cables is not recommended (because of the small size of the pins on the DB-60 serial connector), cable pinouts are provided in the online document Cisco Modular Access Router Cable Specifications. For further information, see the "Obtaining Documentation" section on page viii. About Data Rates and Distance Limitations All serial signals are subject to distance limits, beyond which the signal degrades significantly or is completely lost. Generally, the slower the data rate, the greater the distance. Table 5-3 lists recommended maximum speeds and distances for each serial interface type. If you understand and compensate for potential electrical problems, you may get good results at speeds and distances greater than those listed. For instance, the recommended maximum rate for V.35 is 2 Mbps, but 4 Mbps is commonly used. Table 5-3 Serial Interface Recommended Maximum Speeds and Distances Data Rate, bps 2400 4800 9600 19200 38400 56000 1544000 (T1) EIA/TIA-232 Distance Feet Meters 200 60 100 30 50 15 25 8 12 4 9 3 - - EIA/TIA-449, -530, -530A, V.35, and X.21 Distance Feet Meters 4100 1250 2050 625 1025 312 500 150 250 75 100 30 50 15 Balanced drivers allow EIA/TIA-449 signals to travel greater distances than EIA/TIA-232 signals. The recommended distance limits for EIA/TIA-449 shown in Table 5-3 are also valid for V.35, X.21, and EIA/TIA-530. Typically, EIA/TIA-449 and EIA/TIA-530 support 2-Mbps rates, and V.35 can support 4-Mbps rates. Asynchronous and Synchronous Serial Module Data Rates The following data-rate limitations apply to the slow-speed serial interfaces found on asynchronous and synchronous serial modules: • The maximum data rate on the slow-speed asynchronous interface is 115.2 kbps. The traffic throughput rate allowed is the full 115.2 kbps, with 10 percent of traffic in the opposite direction. • The maximum data rate for the slow-speed synchronous interface is 128 kbps full duplex. OL-2485-20 Cisco Network Modules Hardware Installation Guide 5-3