Asynchronous Terminal Connections
The chassis provides a console port to connect a terminal or computer for local console access. The port has
an RJ-45 connector and supports RS-232 asynchronous data with distance recommendations that are specified
in the IEEE RS-232 standard. The available baud rate is 115200 bauds.
Interference Considerations
When wires are run for any significant distance, there is a risk of receiving stray signals on the wires as
interference. If interference signals are strong, it results in data errors or equipment damage.
The following sections describe the sources of interference and how to minimize their effects on the chassis.
Electromagnetic Interference
All the equipment that is powered by AC current can propagate electrical energy that can cause EMI and
possibly affect the operation of other equipment. The typical sources of EMI are equipment power cords and
power service cables from electric utilities.
Strong EMI can destroy the signal drivers and receivers in the chassis. It can even create an electrical hazard
by causing power surges through the power lines into installed equipment. These problems are rare, but could
be catastrophic.
To resolve these problems, you need specialized knowledge and equipment that could consume substantial
time and money. However, you can ensure that you have a properly grounded and shielded electrical
environment, paying special attention to the need for electrical surge suppression.
Radio Frequency Interference
When electromagnetic fields act over a long distance, radio frequency interference (RFI) may be propagated.
Building wiring can often act as an antenna, receiving the RFI signals and creating more EMI on the wiring.
If you use a twisted-pair cable in your plant wiring with a good distribution of grounding conductors, the plant
wiring is unlikely to emit radio interference. If you exceed the recommended distances, use a high-quality
twisted-pair cable with one ground conductor for each data signal.
Lightning and AC Power Fault Interference
If signal wires exceed the recommended cabling distances, or if signal wires pass between buildings, you may
encounter a lightning strike on the chassis.
The electromagnetic pulse (EMP) generated by lightning or other high-energy phenomena can couple enough
energy into unshielded conductors and damage or destroy electronic equipment. For such problems, you must
consult with RFI and EMI experts to ensure adequate electrical surge suppression and shielding of signal
cables in your operating environment.
This product requires surge protection as part of the building installation. To comply with the Telcordia
GR-1089 NEBS standard for electromagnetic compatibility and safety, an external surge protective device
(SPD) is required at the AC or DC power service equipment.
Warning
Cisco ASR-920-12SZ-A and Cisco ASR-920-12SZ-D Aggregation Services Router Hardware Installation Guide
22
Prepare for Installation
Asynchronous Terminal Connections
