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Before you install the AccessPro card, read this chapter carefully. It contains important information that will make your installation quicker and easier. This chapter contains the following sections:
Follow these guidelines to ensure general safety:
 | Warning Before working on equipment that is connected to power lines, remove jewelry (including rings, necklaces, and watches). Metal objects will heat up when connected to power and ground and can cause serious burns or weld the metal object to the terminals. (To see translated versions of this warning, refer to the appendix "Translated Safety Warnings.") |
Electrostatic discharge (ESD) is a discharge of stored static electricity that can damage electronic equipment and impair electrical circuitry, resulting in complete or intermittent failures. ESD is increased by the combination of synthetic fibers and dry atmosphere.
Always follow ESD-prevention procedures when removing and replacing components. Ensure that the chassis is electrically connected to earth ground. Wear an ESD-preventive wrist strap, ensuring that it makes good skin contact. Connect the clip to an unpainted surface of the chassis frame to safely channel unwanted ESD voltages to ground. To properly guard against ESD damage and shocks, the wrist strap and cord must operate effectively. If no wrist strap is available, ground yourself by touching the metal part of the chassis. Always follow the guidelines in the preceding section, "Safety Recommendations."
 | Caution Do not touch any exposed contact pins or connector shells of interface ports that do not have a cable attached. If cables are connected at one end only, do not touch the exposed pins at the unconnected end of the cable. |
| Caution Periodically check the resistance value of the antistatic strap, which should be between 1 and 10 megohms (Mohms). |
The ports for the Ethernet or Token Ring, serial, and auxiliary connections are located on the rear panel of the main card and the daughter card. (See Figure 2-1, Figure 2-2, Figure 2-3, and Figure 2-4.)
When you set up the LAN and WAN connections, be aware of the distance limitations and potential electromagnetic interference (EMI) as defined by the EIA. Following are the distance limitation specifications for Ethernet 10BaseT, Token Ring RJ-45, BRI, and serial interfaces.
The distance limitation for the IEEE 802.3 specification is a maximum segment distance of 328 feet (100 meters) at a transmission rate of 10 megabits per second (Mbps).
The distance limitation for the IEEE 802.5 specification is a maximum segment distance of 328 feet (100 meters) at a transmission rate of 4 or 16 Mbps.
The specifications for the ISDN BRI cable are listed in Table 2-1.
| Specification | High-Capacitance Cable | Low-Capacitance Cable |
|---|---|---|
| Resistance (@ 96 kHz1) | 160 ohms/km | 160 ohms/km |
| Capacitance (@ 1 kHz) | 120 nF2/km | 30 nF/km |
| Impedance (@ 96 kHz) | 75 ohms | 150 ohms |
| Wire diameter | 0.024" (0.6 mm) | 0.024" (0.6 mm) |
| Distance limitation | 32.8' (10 m) | 32.8' (10 m) |
| Warning The ISDN connection is regarded as a source of voltage that should be inaccessible to user contact. Users should not attempt to tamper with or open any public telephone operator (PTO)-provided equipment or connection hardware. Any hardwired connection (other than by nonremovable, connect-one-time-only lug) must be made only by PTO staff or suitably trained engineers. (To see translated versions of this warning, refer to the appendix "Translated Safety Warnings.") |
| Warning The ports labeled "Ethernet," "Token Ring," and "AUX" are safety extra-low voltage (SELV) circuits. SELV circuits should only be connected to other SELV circuits. Because the BRI circuits are treated like telephone-network voltage, avoid connecting the SELV circuit to the telephone network voltage (TNV) circuits.(To see translated versions of this warning, refer to the appendix "Translated Safety Warnings.") |
As with all signaling systems, EIA/TIA-232 signals can travel a limited distance at any given bit rate; generally, the slower the data rate, the greater the distance. Table 2-2 shows the standard relationship between baud rate and maximum distance for EIA/TIA-232 signals.
| Data Rate (Baud) | Distance (Feet) | Distance (Meters) |
|---|---|---|
| 2400 | 200 | 60 |
| 4800 | 100 | 30 |
| 9600 | 50 | 15 |
| 1200 | 25 | 7.6 |
| 3400 | 12 | 3.7 |
| Caution If you understand the electrical problems that can arise from violating the speed and distance limitations for EIA/TIA-232, and you can compensate for them, you might be able to get good results at distances greater than those shown in Table 2-2; however, we recommend that you stay within the distances defined by the standard. |
Balanced drivers allow EIA/TIA-449 signals to travel greater distances than EIA/TIA-232 signals. Table 2-3 lists the standard relationship between baud rate and maximum distance for EIA/TIA-449 signals. These limits are also valid for V.35 and X.21.
| Baud Rate | Distance (Feet) | Distance (Meters) |
|---|---|---|
| 2400 | 4,100 | 1,250 |
| 4800 | 2,050 | 625 |
| 9600 | 1,025 | 312 |
| 19200 | 513 | 156 |
| 38400 | 256 | 78 |
| 56000 | 102 | 31 |
| T1, E1 | 50 | 15 |
| Caution The EIA/TIA-449 and V.35 interfaces support data rates up to 2.048 Mbps. Because data may be lost, exceeding this maximum is not recommended. |
When you run cables for any significant distance in an electromagnetic field, interference can occur between the field and the signals on the cables. The construction of terminal plant cabling has two implications:
If you use twisted-pair cables with a good distribution of grounding conductors in your plant cabling, emitted radio interference is unlikely. If you exceed the maximum distances--although we do not recommend that you do this--you will get the best results if you ground the conductor for each data signal.
If you have cables that exceed the recommended distances, or if you have cables that pass between buildings, give special consideration to the effect of lightning strikes or ground loops. The electromagnetic pulse caused by lightning or other high-energy phenomena can easily generate enough energy into unshielded conductors to destroy electronic devices. If your site has experienced this kind of problem, consult experts in lightning suppression and shielding.
| Warning Do not work on the system or connect or disconnect cables during periods of lightning activity. (To see translated versions of this warning, refer to the appendix "Translated Safety Warnings.") |
Most data centers cannot resolve the infrequent but potentially catastrophic problems just described without pulse meters and other special equipment. Take precautions to avoid these problems by providing a properly grounded and shielded environment, and pay special attention to issues of electrical surge suppression.
To predict and remedy strong EMI, consult experts in radio frequency interference (RFI).
Access to the console port interface is available through the ISA bus using terminal emulation software running on the PC. To configure the card for console port functionality, refer to the section "Setting COMport Jumpers" in the chapter "Maintaining the AccessPro PC Card."
An RJ-45, asynchronous serial, auxiliary port is included on all AccessPro cards. This is a DTE port to which you can attach a CSU/DSU or protocol analyzer for network access. This port connects to external equipment using an RJ-45-to-DB-25 adapter, shown in Figure 2-5. The appendix "Cabling Specifications" lists the pinouts for the auxiliary port.
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