Cisco 3800 Series - Manual (Page 59)

Connecting a Console or Modem
29
Connecting Cables to Cisco 3800 Series Routers
OL-5970-02
For cable pinouts, see the Cisco Modular Access Router Cable Specifications document.
Warning Do not work on the system, or connect or disconnect cables during periods of lightning activity.
Statement 1001
Warning The ISDN connection is regarded as a source of voltage that should be inaccessible to user contact.
Do not attempt to tamper with or open any public telephone operator (PTO)-provided equipment or
connection hardware. Any hardwired connection (other than by a nonremovable,
connect-one-time-only plug) must be made only by PTO staff or suitably trained engineers.
Statement 23
Warning To avoid electric shock, do not connect safety extra-low voltage (SELV) circuits to telephone-network
voltage (TNV) circuits. LAN ports contain SELV circuits, and WAN ports contain TNV circuits. Some
LAN and WAN ports both use RJ-45 connectors. Use caution when connecting cables. Statement 1021
Warning Hazardous network voltages are present in WAN ports regardless of whether power to the router is
OFF or ON. To avoid electric shock, use caution when working near WAN ports. When detaching
cables, detach the end away from the router first. Statement 1026
Connecting a Console or Modem
Cisco 3800 series routers provide EIA/TIA-232 asynchronous serial console and auxiliary ports. These
ports provide administrative access to the router either locally, using an ASCII terminal or PC running
HyperTerminal or similar terminal emulation software connected to the console port, or remotely, using
a modem connected to the auxiliary port.
The principal difference between the console and auxiliary ports is that the auxiliary port supports
hardware flow control, but the console port does not. Flow control paces the transmission of data
between a sending device and a receiving device, ensuring that the receiving device can absorb the data
sent to it before the sending device sends more. When the buffers on the receiving device are full, a
message is sent to the sending device to suspend transmission until the data in the buffers has been
processed.
Because the auxiliary port supports flow control, it is best suited for use with the high-speed
transmissions of a modem. Terminals send data at slower speeds than modems; therefore, the console
port is best suited for use with terminals.
Cisco provides the following cables and adapters for connecting the router to a console or modem:
• Console adapter cable (RJ-45-to-DB-9, light blue)
• Modem adapter cable (RJ-45-to-DB-25, black)