<s>
Prestel	B-General_Concept
(	O
abbrev	O
.	O
</s>
<s>
from	O
press	B-General_Concept
telephone	I-General_Concept
)	O
,	O
the	O
brand	O
name	O
for	O
the	O
UK	O
Post	O
Office	O
Telecommunications	O
's	O
Viewdata	B-Application
technology	O
,	O
was	O
an	O
interactive	O
videotex	B-Operating_System
system	O
developed	O
during	O
the	O
late	O
1970s	O
and	O
commercially	O
launched	O
in	O
1979	O
.	O
</s>
<s>
Prestel	B-General_Concept
was	O
created	O
based	O
on	O
the	O
work	O
of	O
Samuel	O
Fedida	O
at	O
the	O
then	O
Post	O
Office	O
Research	O
Station	O
in	O
Martlesham	O
,	O
Suffolk	O
.	O
</s>
<s>
As	O
part	O
of	O
the	O
privatisation	O
of	O
British	O
Telecom	O
,	O
the	O
team	O
were	O
moved	O
into	O
a	O
"	O
Prestel	B-General_Concept
Division	O
"	O
of	O
BT	O
.	O
</s>
<s>
Prestel	B-General_Concept
databases	O
is	O
commonly	O
referred	O
to	O
as	O
the	O
'	O
tree	O
structure	O
 '	O
.	O
</s>
<s>
The	O
public	O
Prestel	B-General_Concept
database	O
consisted	O
of	O
a	O
set	O
of	O
individual	O
frames	O
,	O
which	O
were	O
arranged	O
in	O
24	O
lines	O
of	O
40	O
characters	O
each	O
,	O
similar	O
to	O
the	O
display	O
used	O
by	O
the	O
Ceefax	O
and	O
ORACLE	O
teletext	O
services	O
provided	O
by	O
the	O
BBC	O
and	O
ITV	O
television	O
companies	O
.	O
</s>
<s>
Single	O
and	O
double	O
digit	O
pages	O
were	O
special	O
pages	O
reserved	O
by	O
Prestel	B-General_Concept
for	O
general	O
system	O
information	O
purposes	O
,	O
as	O
were	O
the	O
1nn-199nn	O
sets	O
of	O
three	O
digit	O
nodes	O
e.g.	O
</s>
<s>
page	O
1a	O
was	O
the	O
standard	O
Prestel	B-General_Concept
Main	O
Index	O
.	O
</s>
<s>
e.g.	O
,	O
page	O
92	O
showed	O
details	O
of	O
the	O
users	O
Prestel	B-General_Concept
bill	O
,	O
and	O
page	O
910	O
gave	O
IPs	O
access	O
to	O
online	O
editing	O
facilities	O
.	O
</s>
<s>
This	O
layout	O
was	O
later	O
formalised	O
in	O
the	O
1981	O
CEPT	O
videotex	B-Operating_System
standard	O
as	O
the	O
CEPT3	B-Device
profile	O
.	O
</s>
<s>
Because	O
the	O
Prestel	B-General_Concept
system	O
was	O
originally	O
designed	O
to	O
be	O
operated	O
solely	O
by	O
means	O
of	O
a	O
simple	O
numeric	O
keypad	O
it	O
was	O
not	O
possible	O
to	O
access	O
frames	O
other	O
than	O
the	O
top	O
level	O
frame	O
directly	O
(	O
i.e.	O
,	O
in	O
this	O
case	O
pages	O
other	O
than	O
"	O
7471a	O
"	O
)	O
.	O
</s>
<s>
This	O
follow-on	O
frame	O
facility	O
was	O
exploited	O
extensively	O
by	O
the	O
implementation	O
of	O
telesoftware	O
on	O
Prestel	B-General_Concept
whereby	O
computer	O
programmes	O
,	O
notably	O
for	O
the	O
BBC	B-Device
Micro	I-Device
,	O
were	O
available	O
for	O
download	O
from	O
Prestel	B-General_Concept
.	O
</s>
<s>
For	O
standard	O
users	O
,	O
this	O
would	O
be	O
page	O
1a	O
,	O
the	O
general	O
top	O
level	O
index	O
to	O
the	O
whole	O
of	O
Prestel	B-General_Concept
.	O
</s>
<s>
However	O
,	O
if	O
a	O
user	O
signed	O
up	O
through	O
,	O
or	O
later	O
joined	O
,	O
products	O
or	O
services	O
from	O
major	O
IPs	O
,	O
such	O
as	O
Club	O
403	O
,	O
Micronet	O
800	O
,	O
Prestel	B-General_Concept
Travel	O
,	O
CitiService	O
,	O
etc.	O
,	O
they	O
would	O
be	O
given	O
a	O
different	O
welcome	O
page	O
,	O
so	O
that	O
after	O
logon	O
they	O
were	O
routed	O
directly	O
to	O
800a	O
,	O
403a	O
,	O
747a	O
etc	O
.	O
</s>
<s>
From	O
1987	O
onwards	O
,	O
it	O
became	O
possible	O
to	O
use	O
access	O
Prestel	B-General_Concept
pages	O
via	O
use	O
of	O
special	O
alphabetic	O
codes	O
,	O
provided	O
that	O
the	O
IP	O
who	O
owned	O
the	O
page	O
set	O
up	O
a	O
special	O
keyword	O
mapped	O
onto	O
that	O
page	O
.	O
</s>
<s>
With	O
a	O
view	O
to	O
supporting	O
the	O
planned	O
major	O
expansion	O
programme	O
,	O
a	O
new	O
Prestel	B-General_Concept
infrastructure	O
was	O
designed	O
around	O
two	O
different	O
types	O
of	O
data	O
centre	O
:	O
Update	O
Centre	O
(	O
UDC	O
)	O
,	O
where	O
IPs	O
could	O
create	O
,	O
modify	O
and	O
delete	O
their	O
pages	O
of	O
information	O
,	O
and	O
Information	O
Retrieval	O
Centre	O
(	O
IRC	O
)	O
,	O
which	O
mirrored	O
copy	O
of	O
the	O
pages	O
is	O
provided	O
to	O
end-users	O
.	O
</s>
<s>
In	O
those	O
early	O
days	O
of	O
the	O
public	O
service	O
all	O
the	O
live	O
Prestel	B-General_Concept
computers	O
were	O
located	O
in	O
St	O
Alphage	O
House	O
,	O
a	O
1960s	O
office	O
block	O
on	O
Fore	O
Street	O
in	O
the	O
City	O
of	O
London	O
.	O
</s>
<s>
Both	O
types	O
of	O
machine	O
,	O
together	O
with	O
other	O
development	O
hardware	O
,	O
remained	O
in	O
service	O
there	O
until	O
1994	O
when	O
the	O
Prestel	B-General_Concept
service	O
was	O
sold	O
by	O
BT	O
to	O
a	O
private	O
company	O
.	O
</s>
<s>
Exchange	O
buildings	O
were	O
ideally	O
suited	O
to	O
housing	O
the	O
large	O
numbers	O
of	O
rack	B-Application
mounted	I-Application
1200/75	O
baud	O
modems	B-Application
and	O
associated	O
cabling	O
as	O
well	O
as	O
the	O
racks	O
of	O
16-port	O
Multi-Channel	O
Asynchronous	O
Communications	O
Control	O
Units	O
(	O
MCACCUs	O
)	O
or	O
multiplexors	B-Protocol
from	O
GEC	B-Device
which	O
gave	O
the	O
modems	B-Application
logical	O
access	O
into	O
the	O
computers	O
.	O
</s>
<s>
In	O
the	O
new	O
infrastructure	O
,	O
IRCs	O
were	O
connected	O
to	O
the	O
UDC	O
in	O
a	O
star	B-Architecture
network	I-Architecture
configuration	O
,	O
originally	O
via	O
leased	O
line	O
permanent	O
(	O
not	O
packet	O
switched	O
)	O
connections	O
,	O
based	O
on	O
the	O
X.25	B-Protocol
protocol	O
,	O
operating	O
at	O
2.4	O
kilobits	O
per	O
second	O
(	O
kbit/s	O
)	O
.	O
</s>
<s>
By	O
mid	O
1981	O
,	O
these	O
private	O
circuit	O
links	O
had	O
been	O
replaced	O
with	O
dedicated	O
4-wire	O
X25	O
circuits	O
over	O
the	O
new	O
public	O
Packet	B-Protocol
Switch	I-Protocol
Stream	I-Protocol
(	O
PSS	O
)	O
network	O
operating	O
at	O
4.8	O
kbit/s	O
.	O
</s>
<s>
Fully	O
equipped	O
IRC	O
machines	O
had	O
a	O
design	O
capacity	O
of	O
200	O
user	O
ports	B-Protocol
each	O
but	O
these	O
first	O
ten	O
machines	O
were	O
initially	O
only	O
capable	O
of	O
supporting	O
approximately	O
1,000	O
users	O
between	O
them	O
,	O
expandable	O
later	O
to	O
2,000	O
users	O
.	O
</s>
<s>
By	O
September	O
1980	O
,	O
there	O
were	O
five	O
IRC	O
machines	O
in	O
London	O
plus	O
pairs	O
of	O
machines	O
at	O
Birmingham	O
,	O
Nottingham	O
,	O
Edinburgh	O
,	O
Glasgow	O
,	O
Manchester	O
,	O
Liverpool	O
and	O
Belfast	O
offering	O
a	O
total	O
of	O
914	O
user	O
ports	B-Protocol
.	O
</s>
<s>
In	O
some	O
of	O
these	O
locations	O
where	O
there	O
was	O
insufficient	O
Prestel	B-General_Concept
traffic	O
to	O
warrant	O
siting	O
an	O
IRC	O
computer	O
,	O
the	O
plans	O
were	O
to	O
site	O
multiplex	O
equipment	O
in	O
a	O
suitable	O
exchange	O
building	O
from	O
where	O
connections	O
were	O
made	O
over	O
X25	O
to	O
the	O
nearest	O
proper	O
IRC	O
.	O
</s>
<s>
As	O
at	O
the	O
end	O
of	O
1980	O
,	O
there	O
was	O
actually	O
a	O
total	O
of	O
1500	O
live	O
computer	B-Protocol
ports	I-Protocol
available	O
and	O
by	O
July	O
1981	O
,	O
the	O
number	O
of	O
IRC	O
computers	O
has	O
been	O
expended	O
to	O
18	O
,	O
increasing	O
the	O
coverage	O
of	O
the	O
telephone	O
subscriber	O
population	O
from	O
30%	O
to	O
62%	O
.	O
</s>
<s>
In	O
1982	O
,	O
using	O
the	O
multiplexor	B-Protocol
technique	O
described	O
above	O
,	O
a	O
virtual	O
IRC	O
was	O
created	O
in	O
Boston	O
,	O
Massachusetts	O
giving	O
access	O
to	O
a	O
machine	O
in	O
the	O
UK	O
known	O
as	O
Hogarth	O
in	O
order	O
to	O
provide	O
Prestel	B-General_Concept
services	O
to	O
subscribers	O
from	O
across	O
the	O
United	O
States	O
via	O
the	O
Telenet	O
packet	O
switching	O
network	O
.	O
</s>
<s>
The	O
Prestel	B-General_Concept
Mailbox	O
service	O
was	O
originally	O
launched	O
on	O
Enterprise	O
computer	O
to	O
support	O
messaging	O
solely	O
between	O
users	O
on	O
that	O
machine	O
and	O
by	O
1984	O
,	O
the	O
facility	O
had	O
been	O
rolled	O
out	O
nationwide	O
.	O
</s>
<s>
This	O
required	O
a	O
further	O
type	O
of	O
Prestel	B-General_Concept
computer	O
dedicated	O
to	O
the	O
exchange	O
of	O
messages	O
.	O
</s>
<s>
Originally	O
Prestel	B-General_Concept
IRC	O
computers	O
were	O
directly	O
dialled	O
by	O
means	O
of	O
an	O
ordinary	O
telephone	O
number	O
(	O
e.g.	O
,	O
the	O
Enterprise	O
computer	O
in	O
Croydon	O
was	O
accessed	O
by	O
dialling	O
01	O
686	O
0311	O
.	O
</s>
<s>
In	O
1987	O
,	O
the	O
entire	O
local	O
access	O
network	O
was	O
being	O
overhauled	O
and	O
shared	O
with	O
other	O
Dialcom	O
Group	O
companies	O
–	O
users	O
connecting	O
and	O
not	O
automatically	O
logging	O
into	O
Prestel	B-General_Concept
would	O
be	O
greeted	O
with	O
a	O
menu	O
allowing	O
access	O
to	O
Prestel	B-General_Concept
,	O
Telecom	O
Gold	O
,	O
etc	O
.	O
</s>
<s>
Prestel	B-General_Concept
computers	O
were	O
based	O
on	O
GEC	B-Device
4000	I-Device
series	I-Device
minicomputer	B-Architecture
with	O
small	O
differences	O
in	O
the	O
accumulation	O
according	O
to	O
the	O
function	O
of	O
the	O
machine	O
.	O
</s>
<s>
IRC	O
main	O
machines	O
were	O
originally	O
GEC	B-Device
4082	O
equipped	O
with	O
384	O
Kbytes	O
memory	O
core	O
store	O
machines	O
,	O
six	O
70	O
Mbyte	O
HDD	B-Device
and	O
100	O
ports	B-Protocol
for	O
1500	O
initial	O
users	O
.	O
</s>
<s>
The	O
ten	O
computers	O
could	O
output	O
to	O
approximately	O
1000	O
user	O
ports	B-Protocol
,	O
expandable	O
to	O
2000	O
.	O
</s>
<s>
The	O
GEC	B-Device
4082	O
computer	O
with	O
512	O
megabyte	O
capacity	O
will	O
interconnect	O
to	O
the	O
10	O
and	O
later	O
to	O
20	O
retrieval	O
computers	O
to	O
handle	O
the	O
data	O
files	O
.	O
</s>
<s>
Each	O
IRC	O
computer	O
was	O
configured	O
with	O
208	O
ports	B-Protocol
and	O
so	O
was	O
able	O
to	O
support	O
200	O
simultaneous	O
Prestel	B-General_Concept
users	O
,	O
the	O
remaining	O
8	O
ports	B-Protocol
being	O
used	O
for	O
test	O
and	O
control	O
functions	O
.	O
</s>
<s>
Access	O
for	O
the	O
ordinary	O
user	O
was	O
provided	O
via	O
the	O
duplex	O
asynchronous	O
interface	O
provided	O
by	O
banks	O
of	O
GEC	B-Device
16-port	O
multi-channel	O
asynchronous	O
control	O
units	O
(	O
MCACCU	O
)	O
known	O
more	O
simply	O
as	O
multiplexers	B-Protocol
.	O
</s>
<s>
These	O
devices	O
in	O
turn	O
were	O
accessed	O
via	O
banks	O
of	O
standard	O
Post	O
Office	O
Modems	B-Application
No	O
.	O
</s>
<s>
As	O
seen	O
in	O
1979	O
,	O
it	O
had	O
important	O
strengths	O
and	O
weaknesses	O
:	O
"	O
The	O
strengths	O
of	O
viewdata	B-Application
include	O
its	O
visual	O
attractiveness	O
,	O
its	O
ease	O
of	O
use	O
,	O
low	O
cost	O
and	O
its	O
wide	O
range	O
of	O
applications	O
.	O
</s>
<s>
How	O
rapidly	O
viewdata	B-Application
will	O
become	O
established	O
,	O
and	O
the	O
exact	O
role	O
it	O
will	O
fulfil	O
,	O
is	O
as	O
yet	O
a	O
matter	O
of	O
speculation.	O
"	O
</s>
<s>
In	O
addition	O
to	O
the	O
MCACCU	O
units	O
required	O
to	O
support	O
1200/75	O
dial	O
up	O
access	O
,	O
the	O
Update	O
Centre	O
machines	O
were	O
also	O
connected	O
to	O
special	O
modems	B-Application
provided	O
to	O
support	O
online	O
bulk	O
updating	O
by	O
IPs	O
.	O
</s>
<s>
Banks	O
of	O
300/300	O
bit/s	O
full	O
duplex	O
asynchronous	O
V21	O
modems	B-Application
supported	O
computer	O
to	O
computer	O
links	O
for	O
the	O
more	O
sophisticated	O
IP	O
while	O
1200	O
bit/s	O
half	O
duplex	O
V23	O
modems	B-Application
supported	O
so	O
called	O
intelligent	O
editing	O
terminals	O
(	O
i.e.	O
</s>
<s>
Although	O
technically	O
categorised	O
as	O
minicomputers	B-Architecture
,	O
these	O
GEC	B-Device
machines	O
were	O
physically	O
very	O
large	O
by	O
today	O
's	O
standards	O
,	O
each	O
occupying	O
several	O
standard	O
communications	B-Application
cabinets	I-Application
,	O
each	O
standing	O
high	O
by	O
wide	O
.	O
</s>
<s>
The	O
CDC	B-Architecture
9762	I-Architecture
hard	B-Device
disc	I-Device
drives	I-Device
were	O
housed	O
separately	O
in	O
large	O
stand-alone	O
units	O
,	O
each	O
one	O
about	O
the	O
size	O
of	O
a	O
domestic	O
washing	O
machine	O
.	O
</s>
<s>
(	O
See	O
images	O
in	O
the	O
photo	O
of	O
the	O
GEC	B-Device
Computers	I-Device
 '	I-Device
Development	I-Device
Centre	I-Device
)	O
.	O
</s>
<s>
The	O
70	O
Mbyte	O
capacity	O
hard	B-Device
discs	I-Device
themselves	O
were	O
in	O
fact	O
removable	O
units	O
,	O
each	O
consisting	O
of	O
a	O
stack	O
of	O
five	O
14-inch	O
platters	B-Device
,	O
standing	O
high	O
,	O
that	O
could	O
be	O
lifted	O
in	O
and	O
out	O
of	O
the	O
drive	O
unit	O
.	O
</s>
<s>
The	O
GEC	B-Device
machines	O
cost	O
in	O
excess	O
of	O
£	O
200,000	O
each	O
at	O
GEC	B-Device
standard	O
prices	O
,	O
in	O
addition	O
to	O
which	O
there	O
were	O
the	O
costs	O
of	O
all	O
the	O
associated	O
communications	O
equipment	O
.	O
</s>
<s>
GEC	B-Device
4000	I-Device
series	I-Device
computers	O
were	O
capable	O
of	O
running	O
a	O
number	O
of	O
operating	O
systems	O
but	O
in	O
practice	O
Prestel	B-General_Concept
machines	O
exclusively	O
ran	O
OS4000	B-Operating_System
which	O
itself	O
was	O
developed	O
by	O
GEC	B-Device
.	O
</s>
<s>
This	O
in	O
turn	O
supported	O
BABBAGE	B-Device
,	O
the	O
so-called	O
high	O
level	O
assembler	O
language	O
in	O
which	O
all	O
the	O
Prestel	B-General_Concept
software	O
for	O
both	O
IRC	O
and	O
UDC	O
machines	O
(	O
and	O
later	O
the	O
messaging	O
machine	O
)	O
was	O
written	O
.	O
</s>
<s>
In	O
1987	O
,	O
a	O
Prestel	B-General_Concept
Admin	O
computer	O
was	O
introduced	O
which	O
supported	O
the	O
user	O
registration	O
process	O
:	O
the	O
capture	O
of	O
user	O
details	O
from	O
the	O
paper	O
Prestel	B-General_Concept
Application	O
Form	O
(	O
PAF	O
)	O
,	O
the	O
transfer	O
of	O
data	O
to	O
the	O
relevant	O
Prestel	B-General_Concept
computer	O
,	O
and	O
the	O
printing	O
of	O
the	O
welcome	O
letter	O
for	O
users	O
.	O
</s>
<s>
This	O
machine	O
,	O
also	O
based	O
upon	O
GEC	B-Device
4082	O
equipment	O
,	O
was	O
the	O
first	O
to	O
be	O
equipped	O
with	O
1	O
Mbyte	O
of	O
memory	O
which	O
was	O
required	O
to	O
support	O
the	O
Rapport	O
relational	O
database	O
.	O
</s>
<s>
This	O
product	O
from	O
Logica	O
was	O
an	O
early	O
example	O
of	O
deployment	O
of	O
a	O
system	O
written	O
in	O
a	O
4GL	O
database	O
language	O
which	O
supported	O
all	O
features	O
of	O
the	O
Prestel	B-General_Concept
Admin	O
application	O
.	O
</s>
<s>
In	O
order	O
to	O
proactively	O
manage	O
the	O
potentially	O
large	O
numbers	O
of	O
user	O
connections	O
to	O
Prestel	B-General_Concept
computers	O
,	O
special	O
monitoring	O
equipment	O
was	O
developed	O
by	O
Post	O
Office	O
research	O
and	O
development	O
engineers	O
.	O
</s>
<s>
This	O
was	O
known	O
by	O
the	O
acronym	O
VAMPIRE	O
,	O
short	O
for	O
Viewdata	B-Application
Access	O
Monitor	O
and	O
Priority	O
Incident	O
Reporting	O
Equipment	O
–	O
a	O
title	O
which	O
more	O
or	O
less	O
describes	O
its	O
function	O
.	O
</s>
<s>
The	O
device	O
used	O
private	O
circuits	O
to	O
connect	O
modem	B-Application
ports	B-Protocol
on	O
each	O
computer	O
or	O
remote	O
IRC	O
multiplexor	B-Protocol
node	O
,	O
with	O
a	O
display	O
on	O
a	O
television	O
screen	O
Prestel	B-General_Concept
Prestel	B-General_Concept
at	O
the	O
Regional	O
Centre	O
responsible	O
for	O
the	O
administration	O
of	O
IRC	O
.	O
</s>
<s>
The	O
VAMPIRE	O
screen	O
consisted	O
of	O
a	O
matrix	O
of	O
small	O
squares	O
,	O
so	O
arranged	O
that	O
all	O
ports	B-Protocol
for	O
a	O
single	O
IRC	O
computer	O
could	O
be	O
displayed	O
on	O
a	O
single	O
television	O
with	O
each	O
square	O
representing	O
the	O
state	O
of	O
a	O
port	O
simply	O
by	O
means	O
of	O
the	O
colour	O
.	O
</s>
<s>
Free	O
ports	B-Protocol
were	O
shown	O
as	O
green	O
,	O
occupied	O
ports	B-Protocol
as	O
yellow	O
,	O
incoming	O
calls	O
as	O
pale	O
blue	O
and	O
faulty	O
ports	B-Protocol
as	O
red	O
,	O
such	O
that	O
the	O
state	O
of	O
a	O
whole	O
Prestel	B-General_Concept
machine	O
or	O
concentrator	O
node	O
could	O
be	O
determined	O
at	O
a	O
glance	O
.	O
</s>
<s>
This	O
device	O
was	O
never	O
deployed	O
since	O
the	O
number	O
of	O
VAMPIRE	O
sets	O
needed	O
to	O
monitor	O
every	O
Prestel	B-General_Concept
computer	O
and	O
concentrator	O
never	O
got	O
beyond	O
a	O
couple	O
of	O
dozen	O
,	O
spread	O
over	O
many	O
Regional	O
Prestel	B-General_Concept
Centre	O
offices	O
.	O
</s>
<s>
In	O
1983	O
,	O
the	O
Prestel	B-General_Concept
messaging	O
service	O
known	O
as	O
"	O
Prestel	B-General_Concept
Mailbox	O
"	O
was	O
launched	O
,	O
initially	O
hosted	O
on	O
the	O
computer	O
known	O
as	O
"	O
Enterprise	O
"	O
,	O
and	O
later	O
available	O
from	O
all	O
IRC	O
computers	O
by	O
means	O
of	O
a	O
centralised	O
messaging	O
computer	O
known	O
as	O
"	O
Pandora	O
"	O
.	O
</s>
<s>
In	O
order	O
to	O
use	O
the	O
new	O
Prestel	B-General_Concept
Mailbox	O
service	O
,	O
the	O
user	O
went	O
to	O
page	O
*	O
7#	O
which	O
gave	O
access	O
to	O
a	O
set	O
of	O
frames	O
where	O
new	O
"	O
free	O
format	O
"	O
messages	O
could	O
be	O
created	O
,	O
or	O
pre-formatted	O
messages	O
filled	O
out	O
and	O
stored	O
messages	O
could	O
be	O
retrieved	O
,	O
and	O
other	O
related	O
facilities	O
were	O
hosted	O
.	O
</s>
<s>
Prestel	B-General_Concept
Mailbox	O
numbers	O
were	O
generally	O
based	O
upon	O
the	O
last	O
9	O
digits	O
of	O
the	O
user	O
's	O
telephone	O
number	O
,	O
without	O
spaces	O
or	O
punctuation	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
Prestel	B-General_Concept
Mailbox	O
number	O
for	O
Prestel	B-General_Concept
Headquarters	O
which	O
had	O
the	O
telephone	O
number	O
01-822	O
2211	O
would	O
be	O
simply	O
018222211	O
,	O
while	O
that	O
for	O
a	O
user	O
in	O
Manchester	O
with	O
telephone	O
number	O
061-228	O
7878	O
would	O
be	O
612287878	O
.	O
</s>
<s>
In	O
keeping	O
with	O
the	O
established	O
telephone	O
number	O
practice	O
,	O
but	O
unlike	O
the	O
convention	O
with	O
today	O
's	O
internet	O
mailboxes	O
,	O
Prestel	B-General_Concept
Mailbox	O
numbers	O
were	O
published	O
by	O
default	O
,	O
and	O
were	O
available	O
via	O
the	O
Prestel	B-General_Concept
computers	O
in	O
a	O
dedicated	O
directory	O
accessible	O
from	O
page	O
*	O
486#	O
.	O
</s>
<s>
Every	O
time	O
a	O
user	O
logged	O
into	O
Prestel	B-General_Concept
,	O
a	O
Mailbox	O
banner	O
on	O
their	O
Welcome	O
page	O
,	O
usually	O
flashing	O
,	O
would	O
alert	O
them	O
if	O
they	O
had	O
any	O
new	O
messages	O
waiting	O
.	O
</s>
<s>
Telexes	O
could	O
be	O
sent	O
to	O
Prestel	B-General_Concept
Mailbox	O
users	O
from	O
a	O
standard	O
Telex	O
terminal	O
by	O
using	O
Telex	O
Link	O
number	O
and	O
inserting	O
"	O
MBX	O
"	O
and	O
the	O
relevant	O
mailbox	O
number	O
as	O
the	O
first	O
line	O
of	O
the	O
telex	O
message	O
itself	O
.	O
</s>
<s>
The	O
incoming	O
telex	O
message	O
appeared	O
to	O
the	O
Prestel	B-General_Concept
recipient	O
just	O
as	O
an	O
ordinary	O
Mailbox	O
message	O
but	O
with	O
the	O
telex	O
number	O
inserted	O
at	O
the	O
top	O
of	O
the	O
frame	O
.	O
</s>
<s>
Because	O
of	O
the	O
charges	O
inherent	O
in	O
use	O
of	O
the	O
Telex	O
service	O
,	O
messages	O
sent	O
via	O
Prestel	B-General_Concept
Telex	O
Link	O
were	O
chargeable	O
,	O
in	O
1984	O
at	O
the	O
rate	O
of	O
50p	O
for	O
destinations	O
in	O
the	O
UK	O
,	O
£1.00	O
for	O
Europe	O
,	O
£2.00	O
for	O
North	O
America	O
,	O
£3.00	O
for	O
elsewhere	O
and	O
even	O
£5.00	O
for	O
sending	O
to	O
ships	O
via	O
INMARSAT	O
.	O
</s>
<s>
There	O
was	O
no	O
charge	O
to	O
Prestel	B-General_Concept
users	O
for	O
receiving	O
Telex	O
messages	O
.	O
</s>
<s>
In	O
the	O
same	O
year	O
,	O
when	O
there	O
were	O
some	O
70,000	O
users	O
registered	O
,	O
up	O
to	O
100,000	O
mailboxes	O
and	O
telexes	O
were	O
sent	O
each	O
week	O
via	O
Prestel	B-General_Concept
Mailbox	O
.	O
</s>
<s>
A	O
security	O
breach	O
of	O
the	O
Prestel	B-General_Concept
mailbox	O
of	O
Prince	O
Philip	O
,	O
Duke	O
of	O
Edinburgh	O
and	O
subsequent	O
trial	O
led	O
to	O
the	O
Computer	O
Misuse	O
Act	O
1990	O
.	O
</s>
<s>
While	O
teletext	O
services	O
were	O
provided	O
free	O
of	O
charge	O
,	O
and	O
were	O
encoded	O
as	O
part	O
of	O
the	O
regular	O
television	O
transmissions	O
,	O
Prestel	B-General_Concept
data	O
were	O
transmitted	O
via	O
telephone	O
lines	O
to	O
a	O
set-top	O
box	O
terminal	O
,	O
computer	O
,	O
or	O
dedicated	O
terminal	O
.	O
</s>
<s>
While	O
this	O
enabled	O
interactive	O
services	O
and	O
a	O
crude	O
form	O
of	O
e-mail	O
to	O
be	O
provided	O
,	O
gaining	O
access	O
to	O
Prestel	B-General_Concept
also	O
involved	O
purchasing	O
a	O
suitable	O
terminal	O
,	O
and	O
arranging	O
with	O
a	O
Post	O
Office	O
engineer	O
for	O
the	O
installation	O
of	O
a	O
connection	O
point	O
known	O
as	O
a	O
Jack	O
96A	O
.	O
</s>
<s>
(	O
From	O
the	O
early	O
1980s	O
,	O
the	O
"	O
New	O
Plan	O
"	O
sockets	O
were	O
fitted	O
as	O
standard	O
on	O
new	O
lines	O
and	O
on	O
any	O
change	O
of	O
rented	O
handset	O
,	O
and	O
terminals	O
or	O
modems	B-Application
then	O
required	O
no	O
special	O
connections	O
.	O
)	O
</s>
<s>
Each	O
Prestel	B-General_Concept
screen	O
carried	O
a	O
price	O
in	O
pence	O
in	O
the	O
top	O
right-hand	O
corner	O
.	O
</s>
<s>
The	O
original	O
idea	O
was	O
to	O
persuade	O
consumers	O
to	O
buy	O
a	O
modified	O
television	O
set	O
with	O
an	O
inbuilt	O
modem	B-Application
and	O
a	O
keypad	O
remote	O
control	O
in	O
order	O
to	O
access	O
the	O
service	O
,	O
but	O
no	O
more	O
than	O
a	O
handful	O
of	O
models	O
were	O
ever	O
marketed	O
and	O
they	O
were	O
prohibitively	O
expensive	O
.	O
</s>
<s>
Eventually	O
set-top	O
boxes	O
were	O
made	O
available	O
,	O
and	O
some	O
organisations	O
made	O
these	O
available	O
as	O
part	O
of	O
their	O
subscription	O
,	O
for	O
example	O
branded	O
Tandata	O
terminals	O
were	O
provided	O
by	O
the	O
Nottingham	O
Building	O
Society	O
for	O
its	O
customers	O
,	O
who	O
could	O
make	O
financial	B-Application
transactions	I-Application
via	O
Prestel	B-General_Concept
.	O
</s>
<s>
This	O
was	O
particularly	O
problematic	O
with	O
early	O
home	O
modems	B-Application
which	O
used	O
acoustic	B-Device
couplers	I-Device
,	O
because	O
most	O
home	O
phones	O
were	O
hard-wired	O
to	O
the	O
wall	O
at	O
that	O
time	O
.	O
</s>
<s>
Regardless	O
of	O
the	O
hardware	O
choice	O
Prestel	B-General_Concept
was	O
an	O
expensive	O
proposition	O
,	O
and	O
as	O
a	O
result	O
,	O
Prestel	B-General_Concept
only	O
ever	O
gained	O
a	O
limited	O
market	O
penetration	O
among	O
private	O
consumers	O
,	O
achieving	O
a	O
total	O
of	O
just	O
90,000	O
subscribers	O
,	O
with	O
the	O
largest	O
user	O
groups	O
being	O
Micronet	O
800	O
with	O
20,000	O
users	O
and	O
Prestel	B-General_Concept
Travel	O
with	O
6,500	O
subscribers	O
.	O
</s>
<s>
The	O
costs	O
for	O
businesses	O
interested	O
in	O
publishing	O
on	O
Prestel	B-General_Concept
were	O
also	O
expensive	O
.	O
</s>
<s>
During	O
the	O
daytime	O
,	O
when	O
business	O
usage	O
was	O
high	O
,	O
there	O
was	O
a	O
per-minute	O
charge	O
to	O
use	O
Prestel	B-General_Concept
,	O
but	O
in	O
the	O
evenings	O
and	O
weekends	O
,	O
traditionally	O
the	O
quiet	O
times	O
,	O
it	O
was	O
free	O
apart	O
from	O
the	O
telephone	O
call	O
.	O
</s>
<s>
The	O
BT	O
Prestel	B-General_Concept
software	O
development	O
team	O
developed	O
a	O
number	O
of	O
national	O
variants	O
of	O
Prestel	B-General_Concept
,	O
all	O
of	O
which	O
ran	O
on	O
GEC	B-Device
Computers	I-Device
.	O
</s>
<s>
The	O
Singapore	O
system	O
had	O
a	O
notable	O
technology	O
difference	O
in	O
that	O
pages	O
were	O
not	O
returned	O
over	O
the	O
modem	B-Application
connection	O
,	O
but	O
were	O
returned	O
using	O
teletext	O
methods	O
over	O
one	O
of	O
four	O
television	O
channels	O
reserved	O
specially	O
for	O
the	O
purpose	O
,	O
which	O
had	O
all	O
scan	B-Algorithm
lines	I-Algorithm
encoded	O
in	O
teletext	O
format	O
.	O
</s>
<s>
This	O
higher	O
bandwidth	O
enabled	O
use	O
of	O
a	O
feature	O
called	O
Picture	O
Prestel	B-General_Concept
which	O
was	O
used	O
to	O
carry	O
significantly	O
higher	O
resolution	O
pictures	O
than	O
were	O
available	O
on	O
other	O
Prestel	B-General_Concept
systems	O
.	O
</s>
<s>
The	O
original	O
Prestel	B-General_Concept
system	O
,	O
designed	O
for	O
cost	O
effectiveness	O
and	O
simplicity	O
,	O
employed	O
a	O
rudimentary	O
graphic	O
capability	O
known	O
as	O
serial	O
mosaics	O
.	O
</s>
<s>
This	O
command	O
signal	O
,	O
however	O
,	O
physically	O
occupied	O
a	O
blank	O
space	O
on	O
the	O
screen.The	O
French	O
sought	O
to	O
overcome	O
this	O
limitation	O
when	O
they	O
joined	O
the	O
videotex	B-Operating_System
world	O
in	O
the	O
mid-1970s	O
.	O
</s>
<s>
This	O
alphageometric	O
scheme	O
was	O
integrated	O
into	O
the	O
Canadian	O
videotex	B-Operating_System
system	O
which	O
the	O
Canadians	O
referred	O
to	O
as	O
"	O
Telidon	B-Device
"	O
.	O
</s>
<s>
Having	O
developed	O
Prestel	B-General_Concept
as	O
a	O
way	O
of	O
maximising	O
usage	O
of	O
existing	O
telephone	O
lines	O
,	O
the	O
British	O
Post	O
Office	O
and	O
subsequently	O
British	O
Telecom	O
sought	O
to	O
"	O
provide	O
only	O
the	O
framework	O
"	O
for	O
the	O
service	O
,	O
delegating	O
the	O
provision	O
of	O
information	O
to	O
information	O
providers	O
.	O
</s>
<s>
A	O
"	O
mass	O
public	O
service	O
"	O
was	O
envisaged	O
,	O
with	O
considerable	O
public	O
take-up	O
,	O
but	O
a	O
lack	O
of	O
compelling	O
content	O
and	O
services	O
gave	O
domestic	O
users	O
in	O
particular	O
the	O
impression	O
of	O
Prestel	B-General_Concept
being	O
something	O
that	O
"	O
would	O
cost	O
them	O
a	O
lot	O
for	O
relatively	O
little	O
"	O
.	O
</s>
<s>
Thus	O
,	O
Prestel	B-General_Concept
became	O
more	O
like	O
"	O
a	O
fragmented	O
series	O
of	O
computer-linked	O
private	O
systems	O
"	O
used	O
and	O
run	O
by	O
various	O
companies	O
such	O
as	O
American	O
Express	O
and	O
Thomas	O
Cook	O
,	O
for	O
whom	O
adoption	O
of	O
the	O
technology	O
made	O
sense	O
operationally	O
.	O
</s>
<s>
Nevertheless	O
,	O
it	O
was	O
predicted	O
that	O
eventually	O
,	O
"	O
Prestel	B-General_Concept
-	O
or	O
another	O
viewdata	B-Application
system	O
-	O
will	O
be	O
ubiquitous	O
"	O
.	O
</s>
<s>
In	O
contrast	O
to	O
the	O
demise	O
of	O
the	O
British	O
system	O
,	O
the	O
French	O
equivalent	O
of	O
Prestel	B-General_Concept
,	O
Teletel/Minitel	B-Application
,	O
received	O
substantial	O
public	O
backing	O
when	O
millions	O
of	O
Minitel	B-Application
terminals	O
were	O
handed	O
out	O
free	O
to	O
telephone	O
subscribers	O
(	O
causing	O
Alcatel	O
huge	O
financial	O
problems	O
)	O
.	O
</s>
<s>
As	O
a	O
consequence	O
the	O
Teletel	B-Application
network	O
became	O
very	O
popular	O
in	O
France	O
,	O
and	O
remained	O
well	O
used	O
,	O
with	O
access	O
later	O
also	O
possible	O
over	O
the	O
Internet	O
.	O
</s>
<s>
After	O
a	O
short	O
postponement	O
,	O
Minitel	B-Application
closed	O
finally	O
on	O
30	O
June	O
2012	O
.	O
</s>
<s>
In	O
1979	O
the	O
New	O
Opportunity	O
Press	O
launched	O
Careerdata	O
,	O
an	O
interactive	O
graduate	O
recruitment	O
service	O
devised	O
and	O
designed	O
by	O
Anthony	O
Felix	O
,	O
the	O
New	O
Opportunity	O
Press	O
MD	O
,	O
and	O
supported	O
by	O
GEC	B-Device
's	O
Hirst	O
Research	O
centre	O
in	O
Wembley	O
,	O
London	O
,	O
who	O
provided	O
12	O
terminals	O
which	O
were	O
installed	O
in	O
the	O
largest	O
UK	O
university	O
careers	O
advisory	O
services	O
.	O
</s>
<s>
This	O
was	O
the	O
first	O
commercial	O
application	O
on	O
the	O
new	O
medium	O
and	O
was	O
featured	O
in	O
the	O
Prestel	B-General_Concept
Road	O
Show	O
which	O
toured	O
the	O
UK	O
and	O
some	O
European	O
centres	O
.	O
</s>
<s>
A	O
closed-access	O
videotex	B-Operating_System
system	O
based	O
on	O
the	O
Prestel	B-General_Concept
model	O
was	O
developed	O
by	O
the	O
travel	O
industry	O
,	O
and	O
continues	O
to	O
be	O
almost	O
universally	O
used	O
to	O
this	O
day	O
by	O
travel	O
agents	O
throughout	O
the	O
country	O
:	O
see	O
Viewdata	B-Application
.	O
</s>
<s>
The	O
Prestel	B-General_Concept
technology	O
was	O
also	O
sold	O
abroad	O
to	O
several	O
countries	O
,	O
and	O
in	O
1984	O
Prestel	B-General_Concept
won	O
a	O
UK	O
Queen	O
's	O
Award	O
to	O
Industry	O
both	O
for	O
its	O
innovative	O
technology	O
and	O
use	O
of	O
British	O
products	O
(	O
it	O
largely	O
ran	O
on	O
equipment	O
provided	O
by	O
GEC	B-Device
Computers	I-Device
)	O
.	O
</s>
<s>
In	O
1979	O
Michael	O
Aldrich	O
developed	O
an	O
online	O
shopping	O
system	O
,	O
a	O
type	O
of	O
e-commerce	O
,	O
using	O
a	O
modified	O
domestic	O
colour	O
television	O
equipped	O
with	O
the	O
Prestel	B-General_Concept
chipset	O
and	O
connected	O
to	O
a	O
real-time	O
transaction-processing	O
computer	O
via	O
a	O
domestic	O
dial-up	O
telelphone	O
line	O
.	O
</s>
<s>
All	O
the	O
terminals	O
on	O
these	O
systems	O
could	O
also	O
access	O
the	O
Prestel	B-General_Concept
systems	O
.	O
</s>
<s>
The	O
Prestel	B-General_Concept
system	O
was	O
customised	O
and	O
resold	O
by	O
GEC	B-Device
Computers	I-Device
to	O
several	O
other	O
countries	O
,	O
including	O
:	O
Austria	O
,	O
Australia	O
,	O
Germany	O
,	O
Hong	O
Kong	O
,	O
Hungary	O
,	O
Italy	O
,	O
Malaysia	O
,	O
Netherlands	O
,	O
New	O
Zealand	O
,	O
Singapore	O
,	O
and	O
the	O
former	O
Yugoslavia	O
.	O
</s>
<s>
The	O
Singapore	O
system	O
provided	O
a	O
much	O
higher	O
receive	O
bandwidth	O
than	O
was	O
available	O
over	O
dial-up	B-Application
modems	I-Application
at	O
the	O
time	O
by	O
broadcasting	O
the	O
return	O
frames	O
using	O
the	O
Teletext	O
technique	O
of	O
embedding	O
them	O
in	O
broadcast	O
television	O
signals	O
.	O
</s>
<s>
Four	O
VHF	B-Algorithm
TV	O
channels	O
were	O
dedicated	O
to	O
this	O
with	O
all	O
the	O
scan	B-Algorithm
lines	I-Algorithm
used	O
for	O
Teletext	O
encoding	O
,	O
which	O
enabled	O
the	O
system	O
to	O
provide	O
a	O
feature	O
called	O
Picture	O
Prestel	B-General_Concept
to	O
convey	O
higher	O
resolution	O
images	O
.	O
</s>
<s>
The	O
American	O
Viewtron	O
videotex	B-Operating_System
service	O
was	O
modelled	O
after	O
Prestel	B-General_Concept
.	O
</s>
<s>
In	O
1983	O
the	O
UK	O
's	O
first	O
online	B-Application
banking	I-Application
service	O
opened	O
with	O
Homelink	O
,	O
which	O
was	O
a	O
cooperation	O
between	O
the	O
Nottingham	O
Building	O
Society	O
and	O
the	O
Bank	O
of	O
Scotland	O
.	O
</s>
