Education, at every level, is becoming more dependent on technology-the Internet, distance learning, electronic libraries, video conferencing and e-mail-every day. There are initiatives at the national, state and regional levels that are enabling school districts to put telecommunication infrastructures in place to meet these needs.
This newly placed infrastructure means new problems for administrators. Interruptions to computer systems or networks can impact significantly district operations and the availability of educational materials. Therefore, it is essential that local area networks (LANs) connecting a single building within a district, or wide-area networks (WANs) connecting district buildings on a campus or distributed across a region, remain operational at all times.
There are several considerations in protecting the reliability of a communications systems. Frequently, funding for the implementation of technology projects is made available in annual increments, forcing districts to carry out projects in a piece-meal fashion. One key to avoiding disruptions is to plan and implement a cabling infrastructure that will support future networking technologies; allow ease of equipment moves, adds and changes; and remain in place during renovations. With infrastructure and systems in place, the next important step to avoid disruptions is ensuring the reliability and quality of the power supply.
Closeting information To allow the network to operate and expand as needed, the placement of telecommunications equipment rooms and closets, as well as the environmental conditions of these spaces, is critical. The preferred arrangement is one closet per floor, with the closets stacked vertically to maintain the maximum cable length limitations recommended by industry standards.
The following conditions are recommended for main equipment rooms or telecommunications closets where active components spaces are located: -Maintain 64 degrees to 75 degrees F with a relative humidity range of 30 to 55 percent. -Consider a separate HVAC system or controls, since air conditioning usually is required around the clock. -Maintain positive pressure to prevent dust infiltration. -Locate room(s) in a dry location, free of drain pipes and storage. -Allow easy access to backbone cabling system and horizontal cabling. -Avoid close proximity to large electrical equipment such as elevators, motors, transformers, etc., to limit electromagnetic interference. -Size rooms to meet present and future needs.
While these criteria can present challenges in existing buildings, every effort should be made to properly develop the equipment rooms and closet spaces.
The pathways utilized from closets to workstations are another critical planning and design effort. Key issues related to pathway planning are: -Accessibility. -Capacity. -Physical protection. -Aesthetics.
Cable routes Cable trays and conduit systems offer capacity for present and future cabling needs, but must be integrated into building construction and remain accessible. This may not be practical in existing buildings without the benefit of an overall architectural renovation. Surface raceways often are applied to building finishes and present significant challenge to avoid a tacked-on appearance. In the absence of a cable tray or raceway system, many installers propose loose cabling fished through existing wall and ceiling cavities. This approach satisfies budgetary constraints by eliminating the expense of a physical system to support and route cables, but flexibility and performance can be compromised.
Backbone and horizontal cables typically are not self-supporting, and bends, kinks and turns will directly effect transmission characteristics. In addition, a structured pathway system is critical in the administration of the installed infrastructure. Locating and replacing a problem cable is easier when pathways are maintained and cable routing documented.
A backbone cabling system is utilized between telecommunications closets and equipment rooms within and between buildings. The majority of network cable is comprised of horizontal cable, extending from the horizontal cross-connect located in equipment rooms and closets routed to the workstation or work area. The choice of both horizontal and backbone transmission media should relate to proven and popular applications while observing developing trends. Adhering to cabling standards established by ANSI/EIA/TIA and selecting network applications observing these standards is critical to system performance and flexibility.
Power quality Without power, computers-a main part of technology-and other equipment do not work. Therefore, it is vital to employ proper surge suppression.
A coordinated surge suppression system is essential to protect computers and other sensitive electronic network equipment from internal and external power surges. Initial damage to electronic devices occurs if they are subject to a large surge. However, devices frequently continue to operate until subjected to multiple small surges, which eventually cause a failure. The power distribution system should be protected with multiple zones of protection that conform to Underwriters Laboratory listing 1449-98:
-Service entrance-a high ampacity rated suppresser should be located here to attenuate high energy surges that can enter the building.
-Distribution and power panels-a suppresser should be installed at multiple panel locations within the building to attenuate medium energy surges that originate within the building.
-Local or point of use-a quality suppresser should be installed at each computer or electronic device to provide additional surge clamping.
-Data, video and telephone lines-low voltage surge protectors, at the service to the building, equipment rooms and at computer workstations, should be used. Products should all have UL 497 listing.
Another concern is harmonics. The presence of higher frequency power components that are multiples of the primary frequency (60 Hertz) are generated by electronic equipment and stress the power system. Unaddressed, they can cause wiring to overheat and transformers to be overloaded. It is important that older electrical systems are upgraded to handle harmonics properly. The installation of specific equipment to deal with harmonics include:
-Oversized neutral conductors for feeders and branch circuits.
-Harmonic filters to mitigate power quality problems.
-Special electronic-grade panelboards.
-Specification of low-level harmonic generating equipment (ballasts, HVAC drives etc.).
-Special K-rated transformers.
Grounding Careful attention to the grounding system for the power distribution system, building lightning protection system, main computer equipment room, telecommunications closets and computer work station is required.
Black-outs and brown-outs (when the voltage drops to an unacceptable level during periods of peak loading, such as hot summer air-conditioning periods), also cause interruption to computer systems. Solutions to these disruptions include protecting main campus computer rooms by installing UPS (uninterruptible power systems). These systems provide emergency power backup for 5 to 20 minutes, allowing computer technicians to execute an orderly shutdown for longer outages. Schools also may want to consider installing UPS equipment to support other critical equipment, such as the equipment room that serves as the origination point of multi-site distance events.
Long-term power outages require the installation of emergency generators in addition to the UPS, such as required for life-safety systems, critical HVAC or other emergency systems. Generators take a few seconds to start; they cannot be provided in lieu of a UPS.
The Lower Merion School District, located in a Philadelphia suburb, has begun the installation of a carefully planned, high-performance network for telecommunications services within and between 10 schools. The process to develop the network has been administered by Lower Merion's District capital program team, and began with the development of standards for cabling, pathways, telecommunication rooms, and support systems to ensure that the highest level of quality in materials and installation will be maintained in each building.
The district recognized that to protect its investment in technology access, all decisions regarding the network must be measured against established criteria on performance, flexibility and longevity. The Lower Merion High School, a 291,000-square-foot facility serving 1,900 students, is one of two high schools in the district, and was selected to house the district's main equipment rooms providing distributed services to all 10 buildings. A wide area network is planned for installation utilizing an optical fiber backbone to provide high-speed information exchange between sites, while reducing charges from service providers through shared access.
In addition, due to the immediate needs for technology upgrades, both high schools were selected to implement local area networks prior to major renovation projects. This decision required that the infrastructure of cabling, pathways, and spaces be designed to avoid disturbance during the renovations and adapt to the new space requirements after renovations. All backbone and horizontal cabling media types also were carefully specified to support the most progressive networking applications and the increasing demands placed on networks by the multimedia applications utilized in high-school environments.
The quantity of networked equipment within classrooms continues to increase and this situation also was carefully considered. To deal with the enormous quantity of cable, in addition to telecommunications closets, a transition or consolidation point was created utilizing a terminal cabinet located within classrooms, in accordance with newly accepted industry standards. Individual 4-pair Category 5 cables then can be extended to any classroom work area as required, allowing all adds, moves and changes to be accomplished within the room. This greatly facilitates the inevitable function and space changes that will occur during the renovation project, while allowing immediate connectivity needs to be addressed.
Reliable network operation and adequate 120-volt power also was considered by adding new power distribution systems and appropriate bonding and grounding. Each telecommunications closet houses computer-grade panelboards with integral surge suppression and noise filters. The district's main equipment room will receive a new power distribution system with a power conditioner and standby generator