Technical data

Chapter 18 523
T1 Analyzer
Measurement Results
T1 Analyzer
T1 Facility Summary
This next section describes the elements in a typical T1 backhaul facility. Based on
this information, the next section shows typical fault conditions and what
procedures are typically followed to restore service to the T1 span.
With almost no exception all circuits leased from the TELCO are routed through at
least one central office facility. If this were not the case, planning and managing the
repeaters needed for T1 transmission would be an onerous task. Repeater facilities
are need to be spaced at a distance of 6000 feet (about 1.8 km) and generally contain
slots for multiple repeater units. Figure 18-7 shows a typical circuit layout.
Figure 18-7 Typical T1 Circuit Layout
The following definitions apply:
Central Office: This is usually located at the geographic center of a particular
service area. It is normally a building that contains the switching equipment and
cable cross-connect facilities. Although this diagram shows a single central office,
each end is often served by a separate central office. Facilities exist at the central
office to accommodate remote testing and monitoring of T1 facilities.
Field Repeater: Repeaters are necessary when the customer is located beyond 6000
feet (about 1.8 km) from the central office. Multiple repeaters are necessary when
the span exceeds 12000 feet. Most commercial customers are located within 12000
feet (about 3.6 km) of the central office. The repeaters are powered from the central
office. Typically 90 volts is provided between the center-taps of the transmit and
receive transformers. A particular repeater can be looped back by applying a
specific loop-back tone. Often a label affixed to the cabinet denotes the loop-back
tone. This may look like “FLTR A” or “FLTR B”.
NIU: A device provided by the TELCO that contains the necessary equipment to
provide the expected electrical levels to the customer. This device may be active and
the serves as the customer demarcation (demark) point. When this device is active it
can be looped back by applying the proper loop-back code. The customer is