<s>
A	O
peripheral	O
from	O
Sinclair	O
Research	O
for	O
its	O
ZX	B-Operating_System
Spectrum	I-Operating_System
home	O
computer	O
,	O
the	O
ZX	B-Device
Interface	I-Device
1	I-Device
was	O
launched	O
in	O
1983	O
.	O
</s>
<s>
Originally	O
intended	O
as	O
a	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
interface	O
for	O
use	O
in	O
school	O
classrooms	O
,	O
it	O
was	O
revised	O
before	O
launch	O
to	O
also	O
act	O
as	O
the	O
controller	O
for	O
up	O
to	O
eight	O
ZX	B-Device
Microdrive	I-Device
high-speed	O
tape-loop	O
cartridge	O
drives	O
.	O
</s>
<s>
At	O
hardware	O
level	O
it	O
was	O
fundamentally	O
a	O
voltage	O
adaptor	O
,	O
the	O
serial	O
protocol	O
being	O
implemented	O
in	O
software	O
by	O
bit-banging	B-Algorithm
.	O
</s>
<s>
A	O
wedge-shaped	O
device	O
fitting	O
underneath	O
the	O
ZX	B-Operating_System
Spectrum	I-Operating_System
,	O
the	O
ZX	B-Device
Interface	I-Device
1	I-Device
contained	O
of	O
ROM	B-Device
comprising	O
the	O
control	O
software	O
for	O
the	O
Microdrives	O
,	O
an	O
RS-232	O
port	O
and	O
network	O
interface	O
.	O
</s>
<s>
This	O
extended	O
the	O
error	O
handler	O
in	O
the	O
Sinclair	B-Language
BASIC	I-Language
to	O
allow	O
extra	O
keywords	O
to	O
be	O
used	O
.	O
</s>
<s>
As	O
this	O
became	O
an	O
official	O
standard	O
,	O
other	O
developers	O
quickly	O
used	O
this	O
mechanism	O
to	O
create	O
language	O
extensions	O
to	O
Sinclair	B-Language
BASIC	I-Language
.	O
</s>
<s>
These	O
aimed	O
to	O
improve	O
ZX	B-Device
Microdrive	I-Device
cartridge	O
formatting	O
and	O
access	O
time	O
,	O
printing	O
functions	O
via	O
the	O
RS-232	O
interface	O
,	O
and	O
other	O
bugs	O
in	O
the	O
firmware	O
held	O
in	O
the	O
device	O
's	O
internal	O
8K	O
ROM	B-Device
.	O
</s>
<s>
Machine	B-Language
code	I-Language
software	O
which	O
used	O
the	O
officially	O
documented	O
entry	O
points	O
( 	O
 '	O
hook	O
codes	O
 '	O
)	O
would	O
experience	O
few	O
incompatibility	O
issues	O
;	O
however	O
,	O
programs	O
using	O
non-standard	O
entry	O
points	O
risked	O
incompatibility	O
due	O
to	O
the	O
presence	O
of	O
revised	O
entry	O
points	O
.	O
</s>
<s>
The	O
same	O
protocol	O
,	O
renamed	O
QLAN	O
,	O
was	O
later	O
used	O
on	O
the	O
Sinclair	B-Device
QL	I-Device
.	O
</s>
<s>
The	O
ZX	B-Device
Interface	I-Device
1	I-Device
was	O
incompatible	O
with	O
some	O
later	O
ZX	B-Operating_System
Spectrum	I-Operating_System
models	O
such	O
as	O
the	O
+2A	O
and	O
+3	O
,	O
due	O
to	O
differences	O
in	O
ROM	B-Device
and	O
in	O
the	O
expansion	O
connector	O
.	O
</s>
<s>
The	O
device	O
offered	O
two	O
network	O
ports	O
,	O
allowing	O
up	O
to	O
64	O
ZX	B-Operating_System
Spectrums	I-Operating_System
to	O
be	O
daisy-chained	O
using	O
network	O
leads	O
up	O
to	O
long	O
.	O
</s>
