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Before you can install the MGS or C chassis, you must consider and implement certain prerequisites. This chapter includes information on the following preinstallation requirements, with any distinctions between chassis types clearly noted:
To ensure general safety, follow these guidelines:
 | Warning Metal objects will heat up when connected to power and ground. This heated metal can cause serious burns or can weld to a terminal. |
The successful installation of the MGS and C chassis should not require access to the chassis interior; however, if this becomes necessary, the following warning will appear at the beginning of any related procedures:
 | Warning Before accessing the chassis interior, turn off power to the chassis and unplug the power cord. Use extreme caution around the chassis because potentially hazardous voltages are present. |
Failure to observe this warning and act accordingly may result in the potential for shock hazard or electrocution. Before beginning a procedure that requires access to the chassis interior, we strongly advise that you read through the entire procedure. After you read the procedure, if you have any doubts about your ability to perform any part, contact a customer service representative for information on how to proceed.
Following are some basic guidelines when working near electricity:
In addition, use the following guidelines when working with any equipment that might be connected to a power source and is connected to telephone wiring or other network cabling.
Electrostatic discharge (ESD) damage, which occurs when electronic components are improperly handled, can result in complete or intermittent failures. ESD can impair electronic circuitry and equipment. Typically, the successful installation of the MGS or C chassis should not require handling any components; however, always follow ESD prevention procedures.
 | Caution To prevent ESD damage, attach an ESD wrist strap before handling any components. The chassis power cord must be connected, but to prevent shock hazard, the power must be turned off. |
Following are the guidelines for preventing ESD damage:
Step 2 To safely channel unwanted ESD voltages to ground, connect the wrist strap to an unpainted chassis frame surface or another proper grounding point or surface.
Step 3 Use the edge ejectors to remove a card. Handle the card by its sides. Place the card on an antistatic surface or in a static shielding bag. To prevent further damage to the card by ESD voltages, defective cards must remain in the static shielding bag if they will be returned for repair or replacement.
Step 4 Handling the new card by its edges only, insert it into the chassis. Avoid contact between the card and clothing. The wrist strap only protects the card from ESD voltages on the body; ESD voltages on clothing can still damage the card.
Note For safety, periodically check the resistance value of the antistatic strap. The measurement should be within the range of 1 and 10 Mohms.
The MGS and C chassis must be properly installed and maintained to preclude unintended shutdowns. The MGS and C chassis are designed to operate in a level, dry, clean, well-ventilated, and air-conditioned environment. Each chassis has an internal fan (two in the MGS chassis) that pulls air through the card cage and across the power supply. If either the intake or exhaust vents are blocked, this air-cooling function will be impaired, causing the chassis to overheat and possible shut down. Excessive heat can damage the power supply and components.
If the ambient temperature of the air drawn into the chassis is already higher than desirable, the air temperature inside the chassis will also be too high. This condition can occur when the wiring closet or rack in which the chassis is mounted is not ventilated properly, when the exhaust of one chassis (or other electronic device) is placed so that it enters the air intake vent of the chassis, or when the chassis is the top unit in an unventilated rack. Take precautions to avoid these conditions.
The MGS and C chassis can be used as tabletop systems in a data processing or lab environment. The MGS chassis can also be rack mounted. The chassis are intended for unattended or computer room use. Table 2-1 lists environmental design requirements for the MGS and C chassis.
Depending upon the temperature and cooling capability of your site, the chassis will require at least a minimum amount of clearance (approximately 2 to 4 inches in an enclosed rack or closet) on all sides to prevent the chassis from taking in the exhaust (heated) air of other equipment.
Table 2-1 MGS and C Chassis Environmental Specifications
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| 1 All values of relative humidity (RH) are noncondensing. |
The proper location of the MGS or C chassis and the layout of your equipment rack or wiring closet are essential for successful system operation. Equipment placed too close together or inadequately ventilated can cause system malfunctions and possibly shutdowns. In addition, chassis panels made inaccessible by poor equipment placement can make system maintenance difficult.
Read and conform to the following precautions when planning your site layout and equipment locations to help avoid future equipment failures and reduce the likelihood of environmentally caused shutdowns.
Use the Installation Checklist following to assist you with your installation by allowing you to keep track of what was done, by whom, and when. Make a copy of this checklist and make entries as each procedure is completed. Include a copy of the checklist for each system in your Site Log along with your records for the chassis. (See the section "Site Log" on page 2-7.)
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MGS/CGS router name: ________________________________
CPT protocol translator name: _______________________________
Chassis serial number: _________________________________
The Site Log provides a historical record of all actions relevant to the MGS or C chassis system. Keep the Site Log near the chassis where anyone who performs tasks has access to it. Site Log entries might include the following:
Following are the tools and equipment required to attach the rack-mount or slide-mount kit to the MGS chassis and to install both the MGS and C chassis:
When setting up your system, you must consider a number of factors related to the cabling required for your console terminal connections. When using RS-232 connections, be aware of the distance limitations for signaling; electromagnetic interference may also be a factor. For telco (telephone company) connections, there are a variety of modular connectors from which to choose. Each of these cabling considerations is described in the following sections.
A variety of similar signaling schemes use the name RS-232. The following scheme, which is used in all modular and fixed-configuration products, is sufficient to control most modems and hardware flow-control schemes. This scheme provides six signals per line, two of them outputs:
The line drivers are supplied with bipolar 12 volt (V) power; an open output signal will be near +12 or -12V. The Receive Data input has a 10,000-ohm resistor to the -12V supply that helps prevent open lines from ringing and causing spurious input to the router. An open Receive Data line will be near -7V, but can vary from -6 to -10V, depending on temperature and component variation.
The length of your networks and the distance between connections depends on the type of signal, the signal speed, and the transmission media (the type of cable used to transmit the signals). For example, standard coaxial cable has a greater channel capacity than twisted-pair cabling. The distance and rate limits in these descriptions are the IEEE recommended maximum speeds and distances for signaling. You can usually get good results at speeds and distances far greater than these; however, the greater-than-maximum distances are not recommended.
For instance, the recommended maximum rate for V.35 is 2 megabits per second (Mbps), but is commonly used at 4 Mbps without any problems. If you understand the electrical problems that might arise and can compensate for them, you should get good results with rates and distances greater than those shown here; however, do so at your own risk.
The following distance limits are provided as guidelines for planning your network connections before installation.
The maximum distance for Ethernet network segments and connections depends on the type of transmission cable used. The unshielded twisted-pair (UTP) cabling used with 10BaseT is suitable for voice transmission, but may incur problems at 10-Mbps data rates. UTP cabling does not require the fixed spacing between connections that is necessary with the coax-type connections. Table 2-2 lists the IEEE recommendations for the maximum distances between 10BaseT station (connection) and hub.
Table 2-2 Ethernet UTP Maximum Transmission Distances
As with all signaling systems, serial signals can travel a limited distance at any given rate. Generally, the slower the baud rate, the greater the distance. Table 2-3 shows the standard relationship between baud rate and distance for RS-232 signals.
Table 2-3 IEEE Standard RS-232 Transmission Speed Versus Distance
Balanced drivers allow RS-449 signals to travel greater distances than RS-232. Table 2-4 shows the standard relationship between baud rate and distance for RS-449 signals.
Table 2-4 IEEE Standard RS-449 Transmission Speed Versus Distance
The distance limits for RS-449 (listed in Table 2-4), which are also valid for V.35 and X.21, are recommended maximum distances. You can get good results at distances and rates far greater than these. In common practice, RS-449 supports 2-Mbps rates, and V.35 supports 4 Mbps without any problems; however, exceeding these maximum distances is not recommended.
When wires are run for any significant distance in an electromagnetic field, interference can occur between the field and the signals on the wires. This fact has two implications for the construction of terminal plant wiring:
Note To predict and remedy strong electromagnetic interference, you may need to consult experts in radio frequency interference (RFI).
If you use unshielded twisted-pair (UTP) cables in your plant wiring with a good distribution of grounding conductors, the plant wiring is unlikely to emit RFI. When exceeding the distances listed in Table 2-2, use a high-quality twisted-pair cable with one ground conductor for each data signal.
If wires exceed the distances in Table 2-2, or if wires pass between buildings, give special consideration to the effect of a lightning strike in your vicinity. The electromagnetic pulse (EMP) caused by lightning or other high-energy phenomena can easily couple enough energy into unshielded conductors to destroy electronic devices. If you have had problems of this sort in the past, you may want to consult experts in electrical surge suppression and shielding.
Most data centers cannot resolve the infrequent but potentially catastrophic problems just described without pulse meters and other special equipment. These problems can cost a great deal of time to identify and resolve; take precautions to avoid these problems by providing a properly grounded and shielded environment, with special attention to issues of electrical surge suppression.
You must adjust the baud rate of your terminal to match the chassis console and auxiliary port default baud rate of 9600 baud, 8 data bits, no parity, and 2 stop bits. Consult your terminal's documentation for this wiring specification. The console port is a data communications equipment (DCE) device, and the auxiliary port is a data terminal equipment (DTE) device. If necessary, refer to Appendix A, "Cabling Specifications," for the console port and auxiliary port wiring scheme required to connect the chassis to a console terminal or to build your own cables.
Your installation needs will depend on many factors, including the interfaces you plan to use. You may need some of the following data communication equipment to complete your installation:
 | Warning If the voltage indicated on the chassis label is different from the power outlet voltage, do not connect the chassis to that receptacle. A voltage mismatch can cause equipment damage and may pose a fire hazard. |
Table 2-5 lists the components that are included with the shipment of the MGS or C chassis or that are available as options.
Table 2-5 Descriptions of MGS and C Chassis Components
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1 Because it requires a single card cage slot, the CSC-MT card can be used in the MGS chassis only. 2 The slide-mount kit is available as an option only and is not standard equipment. Documentation to install the slide-mount kit is included with its shipment. |
Posted: Thu Nov 6 15:55:26 PST 2003
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