• During the 1980s, a new technology called
ISDN or Integrated Services Digital Network
was developed by BT.
• ISDN makes use of DIGITAL technology.
• It was prohibitively expensive so only
businesses could initially afford it.
As with all new
technology, prices eventually fell and the cost of this technology is now within reach of
homeowners.
technology, prices eventually fell and the cost of this technology is now within reach of
homeowners.
• For domestic users the BT ISDN service is
called 'Home Highway'
• Integrated
Services Digital 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.
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)
-Broadband-ISDN
(B-ISDN).
• Integrated Services refers to ISDN's ability to deliver at minimum two simultaneous
connections, in any combination of data, voice, video, and fax, over a single line. Multiple
devices can be attached to the line, and used as needed. That means an ISDN line can
take care of most people's complete communications needs at a much higher
transmission rate,
without forcing the purchase of multiple analog phone lines.
• Integrated Services refers to ISDN's ability to deliver at minimum two simultaneous
connections, in any combination of data, voice, video, and fax, over a single line. Multiple
devices can be attached to the line, and used as needed. That means an ISDN line can
take care of most people's complete communications needs at a much higher
transmission rate,
without forcing the purchase of multiple analog phone lines.
• The
entry level interface to ISDN is the Basic Rate Interface (BRI), a 144 kbit/s
service delivered over a pair of standard telephone copper wires. The 144 kbit/s
rate is broken down into two 64 kbit/s bearer channels ('B' channels) and one
16
kbit/s
signaling channel ('D' channel or Delta channel).
• BRI
is sometimes referred to as 2B+D
ISDN - advantages
ISDN - advantages
An analogue modem allows speeds up to 56
kilobits per second (in theory).
Standard ISDN is 64Kb but it allows speeds of up to 128 kilobits per second if
your ISP supports it.
Standard ISDN is 64Kb but it allows speeds of up to 128 kilobits per second if
your ISP supports it.
• The ISDN service allows you to use
the telephone at the same time – it does not
tie up the line.
tie up the line.
• It is fast to connect –
only a second or so.
ISDN
- disadvantages
•Your main telephone socket has to be
changed to an ISDN box by an engineer.
•Your computer has to be fitted with an
ISDN modem which is more expensive
than a standard modem.
than a standard modem.
•It is more expensive than Dial-up on a
monthly basis.
•Should you move house, you have to pay
for your telephone line to be converted
back again to a normal line.
back again to a normal line.