ADSL (Asymmetric Digital
ADSL (Asymmetric Digital Subscriber Line)
is a technology for transmitting digital information at a high bandwidth
on existing phone lines to homes and businesses. Unlike regular dialup
phone service, ADSL provides continuously-available, "always on"
connection. ADSL is asymmetric in that it uses most of the channel to
transmit downstream to the user and only a small part to receive
information from the user. ADSL simultaneously accommodates analogue
(voice) information on the same line. ADSL is generally offered at
downstream data rates from 512 Kbps to about 6 Mbps. A form of ADSL,
known as Universal ADSL or G.lite, has been approved as a standard by
ADSL was specifically designed to exploit
the one-way nature of most multimedia communication in which large
amounts of information flow toward the user and only a small amount of
interactive control information is returned. Several experiments with
ADSL to real users began in 1996. In 1998, wide-scale installations
began in several parts of the U.S. In 2000 and beyond, ADSL and other
forms of DSL are expected to become generally available in urban areas.
With ADSL (and other forms of DSL), telephone companies are competing
with cable companies and their cable modem services.
Basic Rate Interface (BRI)
|Basic Rate Interface (BRI)
is an ITU-T ISDN multipurpose user interface standard for simultaneous
voice and data services provided over two 64-kb/s bearer channels and
one 16-kb/s data channel (2B+D) access arrangement to each user
location. The B channels are used for voice or user data, and the D
channel is used for any combination of: data, control/signalling and
X.25 packet networking. The two B channels can be bonded together giving
a total data rate of 128 kbit/s. BRI is the kind of ISDN interface most
likely to be found in residential service.
Computer Telephony Integration
|CTI Computer Telephony Integration allows a PABX system handset to
send and receive data fro a PC. This allows a pc to see the phone number
of an incoming call, it will then look for the number in your software
and pop the record associated with the phone number. The system uses
Microsoft CAPI & TAPI protocols.
Direct Dial Index (DDI)
|Direct Dialing In (DDI),
also known as Direct Inward Dialing (DID), is the ability or service
feature for a caller outside a company to call an internal extension
without having to pass through an operator or attendant. In large PBX
systems, the dialed digits are passed down the line from the CO (central
office). The PBX then completes the call. Direct Inward Dialing is often
proposed as Centrex's major feature. But automated attendants (a
specialized form of interactive voice response systems) also provide a
similar service. Direct Dial Index (DDI) numbers are numbers
associated to ISDN telephone lines. Analogue lines are associated with
one phone number, an ISDN line can carry upto a 100 DDI numbers.
Integrated Services Digital Network or Isolated
Subscriber Digital Network (ISDN,
Integrated Services Digital Network
or Isolated Subscriber Digital Network (ISDN),
originally "Integriertes Sprach- und Datennetz"
(German for "Integrated Speech and Data Network"), is a
telephone system network. Prior to the ISDN, the phone
system was viewed as a way to transport voice, with some
special services available for data. The key feature of
the ISDN is that it integrates speech and data on the
same lines, adding features that were not available in
the classic telephone system. There are several kinds of
access interfaces to the ISDN defined: Basic Rate
Interface (BRI), Primary Rate Interface (PRI) and
In the UK, British Telecom (BT) provides ISDN2e (BRI)
as well as ISDN30 (PRI). Until April 2006, they also offered Home
Highway and Business Highway, which are BRI ISDN-based services that
offer integrated analog connectivity as well as ISDN. Later versions of
the Highway products also included built-in USB sockets for direct
computer access. Home Highway has been bought by many home users,
usually for Internet connection, although not as fast as ADSL, because
it was available before ADSL and in places where ADSL does not reach.
Virgin Media also use ISDN lines for customers of Virgin Broadband who
live in cable TV areas.
|Multiple Subscriber Number
(MSN) is an incoming call routing method in which a group of phone
numbers is assigned to a particular PRI ISDN line by the telephone
company. A PRI ISDN line is usually assigned multiple numbers in the US
and in Europe. If you use ISDN lines a name can be assigned to each
Direct Dial Index number so that when a call comes in on company A's
phone number the system handset will display Company A so that the call
be answered accordingly, and vice versa for any other DDI numbers.
POTS (Plain Old Telephone
|Plain Old Telephone Service
(POTS) is the standard, analogue telephone service which remains the
basic form of residential and small business telephone service nearly
everywhere in the world. Plain Old Telephone Service was originally
known as the Post Office Telephone Service in many countries. It has
been available almost since the introduction of the telephone system in
the late 19th century, mostly unchanged to the normal user since then
despite the introduction of electronic telephone exchanges into the
public switched telephone network since the middle of the 20th century.
POTS is a term sometimes used in discussion of new telephone
technologies in which the question of whether and how existing voice
transmission for ordinary phone communication can be accommodated. For
example, Asymmetric Digital Subscriber Line and Integrated Services
Digital Network connections provide some part of their channels for
"plain old telephone service" while providing most of their bandwidth
for digital data transmission.
Primary Rate Interface (PRI)
Primary Rate Interface (PRI) is an
ISDN interface for primary rate access, which consists of a single
64-kbps D channel plus 23 (T1) or 30 (E1) B channels for voice or
data. PRI intended for larger users, such as business users. The
other ISDN interface is the Basic Rate Interface (BRI), which is for
homes and small businesses.
Session Initiation Protocol (SIP)
|Session Initiation Protocol
(SIP) is the IETF's standard for establishing VOIP connections. SIP is
an application layer control protocol for creating, modifying and
terminating sessions with one or more participants. The architecture of
SIP is similar to that of HTTP (client-server protocol). Requests are
generated by the client and sent to the server. The server processes the
requests and then sends a response to the client. A request and the
responses for that request make a transaction.
Telephony Application Programming Interface (TAPI)
||The Telephony Application
Programming Interface (TAPI) is an API developed by Microsoft and Intel,
which enables PCs running Microsoft Windows to use telephone services.
Voice over IP (VOIP)
|Voice over IP
(VOIP) uses the Internet Protocol (IP) to transmit voice as packets over
an IP network. Using VOIP protocols, voice communications can be
achieved on any IP network regardless it is Internet, Intranets or Local
Area Networks (LAN). In a VOIP enabled network, the voice signal is
digitized, compressed and converted to IP packets and then transmitted
over the IP network. VOIP signaling protocols are used to set up and
tear down calls, carry information required to locate users and
negotiate capabilities. The key benefits of Internet telephony (voice
over IP) are the very low cost, the integration of data, voice and video
on one network, the new services created on the converged network and
simplified management of end user and terminals.