Overview This application note clarifies the function of line buildout (LBO) settings in the central office network architecture. LBO Functionality in the Network Line buildout settings are an inherent part of T1 and T3 network element transmission circuitry. Because cable lengths between network elements and DSX vary in the central office, LBO settings are designed to adjust the output power of the transmission signal to achieve equal level point (ELP) at the DSX. Most network elements allow LBO settings to be adjusted via software or hardware settings. Purpose of LBO Settings In the central office network, LBO settings are designed specifically to establish equal level point at the DSX (typically defined as 0dB +/-1.5dB). The "long" and "short" line buildout settings refer to power output levels that correspond to the attenuation characteristics of the cabling between the network element and the DSX. The output power levels associated with LBO settings are not designed to accommodate overall cable lengths (near- end NE to DSX, DSX to DSX and DSX to far- end NE). Central Office Line Buildout Settings and Equal Level Point application note ADC Telecommunications, Inc., P.O. Box 1101, Minneapolis, Minnesota USA 55440-1101 Specifications published here are current as of the date of publication of this document. Because we are continuously improving our products, ADC reserves the right to change specifications without prior notice. At any time, you may verify product specifications by contacting our headquarters office in Minneapolis. ADC Telecommunications, Inc. views its patent portfolio as an important corporate asset and vigorously enforces its patents. Products or features contained herein may be covered by one or more U.S. or foreign patents. 1270299 07/03 Original © 2000 ADC Telecommunications, Inc. All Rights Reserved An Equal Opportunity Employer Web Site: www.adc.com From North America, Call Toll Free: 1-800-366-3891 • Outside of North America: +1-952-938-8080 Fax: +1-952-946-3292 For a complete listing of ADC's global sales office locations, please refer to our web site. By setting the LBOs for all network elements to a standard equal level point at the DSX, service providers are able to cross-connect any two network elements at any point in time and achieve an operational transmission path with predictable results. Using LBO to Bypass Equal Level When a network element is initially cabled to the DSX, the service provider may not know if the circuit will ultimately be handed to another carrier (CLEC) or where the far end equipment will be located in the cen- tral office. It is possible to make a particular signal work by ignoring equal level point at the DSX and adjust- ing LBO settings such that the signal is driven to the far-end receiving equipment. However, this practice has several negative implications for the network. Service providers cannot be assured of "any-to-any" circuit compatibility when cross-connecting. This impacts time-to-service, requiring custom design and field modifications for every circuit in the network. Network restoration operations, such as patching and troubleshooting, are nearly impossible when ELP does not exist at the DSX because circuits cannot be cross-connected with predictable results. It may be necessary to adjust the LBOs to different levels than previously established in order to make a temporary circuit work properly. This could involve significant network down time. In the case of service hand-offs to other carriers (such as CLECs) and customers, there are implications to engineering circuits with the assumption that LBO settings can be modified once the far-end receiving equipment has been assigned. Many regulations state that signals must be handed off at an ELP (0dB +/- 1.5dB) at the central office demarcation point (DSX or ICDF). Oftentimes, the end user equipment is not present when the carrier cables to the demarcation point. If equal level point standards are not designed into the circuit when the carrier cabling is assigned, custom engineering efforts and service delays can occur. Conclusion If LBO settings are used to modify transmission power levels to achieve a desired level at the receiver without consideration of equal level point at the DSX, network standards are compromised. DSX and equal level point are key elements of the T1 and T3 central office network architecture that help to ensure that any circuit can be cross-connected to any other circuit with predictable results. The benefits of this architecture include fast service delivery, and consistent planning, engineering and operational prac- tices regardless of when a network element was placed, who placed the network element, or what type of network elements are being cross-connected. . lengths (near- end NE to DSX, DSX to DSX and DSX to far- end NE). Central Office Line Buildout Settings and Equal Level Point application note ADC Telecommunications,. the function of line buildout (LBO) settings in the central office network architecture. LBO Functionality in the Network Line buildout settings are an