IT FAQs
DSL and telephone terminology
Below is a list of DSL and telephone-related terminologies.
ISDN - Integrated Services Digital Network
Gives a user up to 56 kbps of data bandwidth on
a phone line that is also used for voice, or up
to 128 kbps if the line is only used for data.
POP - Point of Presence
A node of an ISP containing a DSU-CSU, terminal
server and router and sometimes one or more hosts,
but no network information center or network operations
center.
POTS - Plain Old Telephone Service
Basic voice service available in residences throughout
Australia.
TELCO - Telephone Company
Generic name for telephone companies throughout
the world.
LOCAL LOOP
A pair of wires, moderately twisted for the entire
length between the telephone company's end office
and the user premises (the common telephone set)
form a loop, so it is referred to as the local
loop. This loop provides a user with access to
the global telecommunications infrastructure that
is installed all over the world. The local loop
has been historically designed to provide voice
grade audio service. The circuit is powered from
the central office with 48V (open circuit voltage)
limited in current to a value somewhat higher
than 20mA. This current is used for signaling
phone access, burning off moisture, breaking through
metalic oxides caused by corrosion, and powering
a carbon microphone. The original telephone equipment
contained no active electronics. The actual wiring
of the local loop may be considered to be a lossy
transmission line. DSL uses whatever frequencies
will propagate on this line for purposes of digital
data transmission. T1 modulation (alternate mark
inversion) has been doing this for years. DSL
extends the capability by using modern technology
to increase the data rates and distances spanned.
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