Technology in Educational Facilities

Cost is a significant factor in the decision of how best to install network cabling above ceilings in school facilities. The California Electrical Code does not require that data cabling be installed in conduits, provided the cabling is plenum rated. Cable prices generally fall into the following range:

The cost difference between PVC and plenum rated cable should be weighed against the cost of conduit, which generally costs $2.50 to $4.50 per foot. Depending on the cable and conduit diameters, between 4 and 15 cables can be installed in a single conduit, so the conduit cost per cable should be around $0.30 to $0.75 per cable.

In addition, future flexibility should be considered. The ability to re-cable or re-route existing cables may dictate the use of conduits.

Several WAN formats are currently available (or will be soon). These include a number of Dial-up, Switched and Dedicated connection types and services. The major factors for deciding which WAN format to utilize include Cost (both for service and equipment), Data Rate (relative to your needs) and Availability (both that of service type in your area and that of equipment needed to implement the technology). The following is a list of some of the more common WAN services and formats:

• POTS - Plain Old Telephone Service. This method utilizes standard (analog) dial-up telephone services. These are the same lines used to carry normal voice and facsimile traffic, although a separate outside line for data will prevent conflicts with other services. A modem is placed at two remote locations, which connect via the telephone line. Typically one modem acts as a host, while the other modem acts as a remote terminal. Downstream data transmission rates of up to 56,000 bits per second, utilizing the new CCITT V.90 standard, are possible. This is suitable for text and file transfers, image down/uploading and simple remote computing. Real time cd quality audio, video and high end remote client/server applications are not possible at this slow data rate.


• ISDN - Integrated Services Digital Network. Utilizing existing telephone cables, a digital line is established between two or more locations via the local carrier's switching equipment. ISDN will support data transfer, normal voice traffic and facsimile transmissions. Basic Rate Interface (BRI) consists of two data channels and one signaling channel. Primary Rate Interface (PRI) has 23 data channels and a signal channel. Each data channel can support a rate of 64,000 bits per second, and channels may combined to further increase the rate, to a maximum of 128,000 bits per second for BRI and 1,544,000 bits per second foe PRI. ISDN is suitable for file transfers, internet access, application sharing and video conferencing. More information is available at the National ISDN Council Home Page.


• T-1/T-3 - T-Carrier Services. Digital data and voice transmission over special lines, normally leased from the telephone company. T-1 lines provide a signal capacity of up to 1,544,000 bits per second. Fractional T-1 allows customers to lease less than a full T-1 line. Up to 40 channels of 64,000 bits per second each may be used in any increment. T-3 has a capacity of 44,736,000 bits per second. Fractional T-3 is also available. These lines may be dedicated (permanent connection) or switched (connected only when there is active traffic). Switching is normally done by the carrier's equipment. A channel sevice unit (CSU), a data service unit (DSU), and multiplexer and a router are all required to connect the T-carrier line to the Local Area Network at each LAN location.


• Fiber Optic - Increasingly, carriers are starting to offer fiber optic lines between the local exchange and business and/or residential service sites. In the near future data rates as high as 2,488,000,000 bits per second will be available. These rates will allow for virtually any real time applications desired.


• Cable Modem Service - With the recent deregulation of the telecommunications industry, an increasing number of cable telecommunications providers are offering data services over existing media, as well as over newly deployed fiber optic infrastructure. This technology provides downstream data rates as high as 30,000,000 bits per second. It is anticipated that upstream data traffic will be conducted via separate media (e.g. telephony), to maximize available downstream bandwidth. Cable modem applications will be primarily in the realm of video on demand, delivery of cd audio, interative gaming and internet applications (at least initially). More information is available at the Cable Modem Home Page.


• ADSL - Asymmetric Digital Subscriber Line. ADSL utilizes existing telecommunications cabling and provides for a 6,000,000 bits per second (maximum) downstream channel, a 640,000 bits per second (maximum) duplex channel and a POTS channel, all on the same line. While this service is not yet available, it is expected to be within the next year or so. ADSL will be suitable for movies-on-demand, video information retrieval, internet access and high speed data transfers. Additional information is available at the ADSL Forum Home Page.


• ATM - Asynchronous Transfer Mode. An emerging high speed data transmission technology offering thru-put rates as high as 622,000,000 bits per second. ATM is currently being deployed by AT&T and US Sprint, over fiber optic, T-1 and T-3 lines. ATM is suitable for traffic including voice, data, facsimilie, real-time video, cd quality audio and imaging. It interfaces well with LAN applications and a wide variety of ATM interface cards, switches and routers are available. More information is available at the ATM Forum Home Page.


• Frame Relay - Frame relay is an outgrowth of ISDN. It offers data rates from 56,000 bits per second, to as high as 1,544,000 bits ber second. It is currenty available from AT&T, MCI, US Sprint and the seven Regional Bell Operating Companies (RBOCs). Frame relay signals can be transmitted over Fiber Optic, ISDN or T-Carrier lines. It integrates well with LAN applications. More information is available at the Frame Relay Forum.

• CDE K-12 Network Technology Planning Guide
• Information Today
• Internet Week
• Network on the Web
• Technology & Learning Magazine
• Telecommunications Industry Association

• CSFM's Relocatable Classroom Fire Code Requirements
• DSA's Alternative Relocatable School Buildings Approval Procedures
• DSA's Class Size Reduction Program Procedures