A subscriber loop carrier or subscriber line carrier (SLC) provides

telephone exchange A telephone exchange, telephone switch, or central office is a central component of a telecommunications system in the public switched telephone network (PSTN) or in large enterprises. It facilitates the establishment of communication circuits ...

-like

telephone A telephone, colloquially referred to as a phone, is a telecommunications device that enables two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most ...

interface functionality. SLC remote terminals are typically located in areas with a high density of telephone subscribers, such as a residential neighborhood, or very rural areas with widely dispersed customers, that are remote from the telephone company's central office (CO). Two or four T1 circuits (depending on the configuration) connect the SLC remote terminal to the central office terminal (COT), in the case of a universal subscriber loop carrier (USLC). An integrated subscriber loop carrier (ISLC) has its

T-span Digital Signal 1 (DS1, sometimes DS-1) is a T-carrier signaling scheme devised by Bell Labs. DS1 is the primary digital telephone standard used in the United States, Canada and Japan and is able to transmit up to 24 multiplexed voice and data ca ...

s terminating directly in time division switching equipment in the

. One system serves up to 96 customers. This configuration is more efficient than the alternative of having separate copper pairs between each

service termination point In telecommunications, the service termination point is the last point of service rendered by a commercial carrier under applicable tariffs. Usually, the service termination point is on the customer premises and corresponds to the demarcation poin ...

(the subscriber's location) and the central telephone exchange. These systems are generally installed in cabinets that have some form of

uninterruptible power supply An uninterruptible power supply (UPS) or uninterruptible power source is a type of continual power system that provides automated backup electric power to a electrical load, load when the input power source or mains electricity, mains power fai ...

or other backup battery arrangements, standby generators, and sometimes with additional equipment such as remote

DSLAM A digital subscriber line access multiplexer (DSLAM, often pronounced ''DEE-slam'') is a network device, often located in telephone exchanges, that connects multiple customer digital subscriber line (DSL) interfaces to a high-speed digital co ...

Reliability

SLCs have been criticized for reducing the reliability of

local loop In telephony, the local loop (also referred to as the local tail, subscriber line, or in the aggregate as the last mile) is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the co ...

s due to their increased reliance on utility power. Historically, all loop power was provided by the CO and was backed up by battery power and, for longer power outages, stand-by diesel generators housed at the office. However, telephone companies have increasingly been using SLCs, which are notorious for poorly functioning or short-lived battery backup systems, some lasting as little as four hours. Many do not have on-site standby generators, which requires the telephone company to bring out a portable generator before the battery power fails. This may not happen in time if there are obstructions caused by a natural or man-made disaster, causing service outages for anyone served by that unit. Often, the air conditioning units, sump pumps, and even lights are not backed up in those units, which can cause equipment overheating and flooding issues.

References

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Reliability

References

See also