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This chapter recommends general safety guidelines to follow and identifies requirements to meet before going to a subscriber site to install a Cisco uBR910 series cable data service unit (DSU).
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Warning Only trained and qualified personnel should be allowed to install, replace, or service this equipment. |
The chapter includes the following sections:
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Note For information on the governmental regulations and restrictions on this equipment, see "Regulatory Compliance and Safety Information." |
This section describes the general, electrical, and electrostatic discharge guidelines that should be followed when installing the Cisco uBR910 series DSU.
Follow these guidelines to ensure general safety:
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Warning Failure to properly ground the Cisco uBR910 series---either by circumventing the three-wire grounding-type plug or by using a power outlet that is improperly grounded---can create a potentially hazardous electrical situation. |
Follow these guidelines when working with electrical equipment:
In addition, follow these guidelines when working with equipment that is disconnected from a power source, but still connected to cable wiring.
If an electrical accident occurs, proceed as follows:
Electrostatic discharge (ESD) damage, which occurs when electronic cards or components are improperly handled, can result in complete or intermittent system failures. The Cisco uBR910 series DSU consists of a printed circuit board that is housed in an enclosure. Electromagnetic interference (EMI) shielding and connectors are integral components of the enclosure. Although the enclosure helps protect the boards, use an antistatic strap whenever handling the Cisco uBR910 series DSU.
Following are guidelines for preventing ESD damage:
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Caution For safety, periodically check the resistance value of the antistatic strap. The measurement should be between 1 and 10 megohm. |
This section describes the following requirements that must be met before installing the Cisco uBR910 series DSU:
Before going to a subscriber site to install the Cisco uBR910 series DSU, verify that the following have been done:
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Note Cisco recommends that a dedicated (new) CATV cable drop be run from the grounding block directly to the Cisco uBR910 series DSU. If such a drop is not available, careful qualification of existing cable is often necessary. Cable ground should be connected to the grounding system of the building or residence as close to the point of cable entry as practical. For the United States, refer to the National Electrical Code Section 820-40 guidelines for proper grounding. |
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Note Should such a device be installed between the Cisco uBR910 series and the headend, the provisioning process will fail. |
"Technical Specifications" lists the operating and nonoperating environmental site requirements for operation of the Cisco uBR910 series DSU. This appendix shows the minimum and maximum values allowed for proper operation, but if a measurement approaches either the minimum or maximum of a range, it could indicate a potential problem. You can maintain normal operation by anticipating and correcting environmental anomalies before they approach a maximum operating range.
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Caution For proper airflow, keep the back, sides, and bottom of the Cisco uBR910 series DSU clear of obstructions and away from the exhaust of other equipment. To prevent unit overheating, never install the Cisco uBR910 series DSU in an enclosed rack or room that is not properly ventilated or air conditioned. |
The Cisco uBR914 DSU uses an AC-input power supply that supports an optional redundant power supply (RPS). These power supplies contain a power switch, but the Cisco uBR914 is intended to remain on after it is initially installed. Power should be turned off to the Cisco uBR914 only when it is being removed from service or when a router interface module is being upgraded or replaced.
Before applying power to any Cisco uBR910 series DSU, verify that the power source is within the values given in "Technical Specifications."
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Note The AC-input power supply supports both domestic (U.S.) and international operation. Different power cords are required, however, depending on the country of operation. |
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Caution Use only a Cisco-provided power supply and cord. Using any other vendor's power supply and cord can cause loss of data or permanent damage. The Cisco uBR910 series DSU requires power cords applicable to the country of operation. |
When running the coaxial line from the cable TV trunk connection to the subscriber site, consider the issues of electromagnetic interference (EMI), coaxial cable quality, and distance limitations for signaling, as described in the following sections.
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 plant wiring:
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Note Category 5 data wiring and telco wiring is much more susceptible to EMI than high-grade well-shielded coaxial CATV cable. |
If wires exceed recommended distances, or if wires pass between buildings, give special consideration to the effect of a lightning strike in your vicinity. The electromagnetic pulse caused by lightning or other high-energy phenomena can easily couple enough energy into unsaddled conductors to destroy electronic devices. If you have had problems of this sort in the past, you might want to consult experts in electrical surge suppression and shielding.
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Note A 5 dB reduction in signal quality for analog downstream video might cause a slight degradation of picture clarity, which might or might not be noticeable to a subscriber. A 1 dB reduction in signal quality for digital data might completely disrupt service to a Cisco uBR910 series user. |
Check the cables for general quality level, tears or cuts in the insulation, insulation that is at least 80% braid with foil, a broken or bent center conductor at the conductor ends, the length of the center conductor, and splitters or amplifiers that have been added to extend video connectivity at the installation site.
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Note The center conductor should extend 1/8 inch (3.2 mm) beyond the end of the conductor. |
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Tips Cisco recommends that you replace any cable that is in question and begin the installation with clean, two-way digital data transmission media. If the cable is of high-quality and was recently installed, replacing the connectors with high-quality connectors can also improve performance and eliminate future service calls. |
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Note Exceeding this distance is a violation of the DOCSIS RFI specification. |
When preparing a site for network connections to the Cisco uBR910 series DSU, consider the following:
Potential distance limitation problems in the CATV network can be reduced by ensuring the following factors:
Assemble the tools and equipment needed to install the Cisco uBR910 series DSU at subscriber sites. Table 2-1 lists the recommended items that Cisco does not provide.
| Checked Off | Item |
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| The following tools are required for every installation: | |
| If installing the Cisco uBR914 DSU in a rack mount, an installation toolkit that includes the following items:
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| If using the RPS option with the Cisco uBR914 DSU, you must also have the following:
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| The required cables include the following:
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| Portable, hand-held console terminal, such as a laptop computer, with EIA232 serial port, communications software, and a setting of 9600 baud, 8 data bits, no parity, and 1 stop bit (9600 8N1). The terminal is required if you will need to configure the serial interfaces on the Cisco uBR910 series and the access router before connecting the Cisco uBR910 series to the cable network. |
| The following tools are optional, depending on the site requirements: | |
| Signal level meter capable of reading a 64-QAM signal or a spectrum analyzer (HP8594Q or equivalent) as appropriate. An alternative is a clear understanding of the digital-to-analog channel amplitude offset and a calibrated analog signal level meter to measure a nearby adjacent analog carrier. |
| Mixed set of attenuators (pads), cable adapters, splitters, high-pass filters (HPF), directional couplers as appropriate |
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Note A cable console kit and console cable, used to locally reconfigure the Cisco uBR910 series DSU, can be purchased separately. |
The subscriber in-box documentation set includes:
The service provider in-box documentation set includes:
The following additional documents are available on CCO:
Based on the number of subscriber sites you are scheduled to install, ensure that you have sufficient Cisco-provided bulk box packages. After you have completed installation, give each subscriber a copy of the Quick Start, Cisco uBR910 Series Cable DSU Subscriber Setup publication, along with any documentation your company provides.
Posted: Thu Jun 15 10:55:53 PDT 2000
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