User`s manual
Synchronous Idle
(S
Y
N)
-
Character
used
as
a
time
fill
in
the
absence
of
any
data
or
control
character
to
maintain
synchronization.
The
sequence
of
two
con-
tinuous
SYNs
is
used
to
establish
synchronization
(character
phase)
following
each
line
turnaround.
System
Unit -
Three
8-s1ot
connector
blocks
mounted
end-to-end
and
capable
of
accommodating
up
to
four
hex
modules
(printed
circuit
boards).
\Vhen
two
sys-
tem units
are
connected
to
form a
double
system
unit,
up
to
nine hex
modules
may
be
accommodated.
Teletypewriter Exchange Service
(TWX)
-
An
auto-
matic
teleprinter
exchange
switching service
provided
by
Western
Union.
Telex -
An
automatic
teleprinter
exchange
switching
service
provided
by
Western
Union.
Temporary
Text
Delay
(TTD)
- In Binary
Synchro-
nous
Communications,
a
control
character
sequence
(STX ...
ENQ)
sent by a
transmitting
station
to
either
indicate
a delay
in
transmission
or
to
initiate
an
abort
of
the transmission
in
progress.
If'rm
-
'ermtn:tI
Terminal - (a.) A
point
at
which
information
can
enter
or
leave a
communication
network.
(b.)
An
I/O
device designed to receive
or
send
source
data
in
an
environment
associated with
the
job
to
be
performed.
Capable
of
transmitting
entries
to
and
obtaining
out-
put
from the system
of
which it
is
a
part.
Text
-
That
part
of
the
message which
contains
the
substantive
information
to
be
conveyed.
Sometimes
called ""body"
of
the
message.
Transparent Mode -
Transmission
of
binary
data
with
the
recognition
of
most
control
characters
sup-
pressed. In Binary
Synchronous
Communications,
C-5
entry
to
and
exit from
the
transparent
mode
is
indicated
by a
sequence
beginning with a special
Data
Link Escape
(OLE)
character.
TTD
-
Temporary
Text
Delay (q.v.).
Unihus -
The
single,
asynchronous,
high-speed
bus
structure
shared
by
the
PDP-II
processor,
its
memo-
ry,
and
all
of
its peripherals.
Unihus
Load
-
The
electrical
connection
of
two
8881
outputs
and
one
8640
input
to
a
Unibus
signal lead.
Unit
Load
- All
inputs
impose
a
load
on
the
outputs
driving
them.
A
TTL
unit
load
requires 1.6 rnA
at
ground
and
+40
J,LA
at
+3
V.
The
load
imposed
upon
an
output
by
an
input
can
be defined as a
number
of
unit loads.
Vector -
Two
words,
containing
the
value
of
the
pro-
gram
counter
and
processor
status
word,
respective-
ly,
that
direct
the
processor
to
a new
routine.
Vector Address -
The
address
of
the
location
contain-
ing
the
vector
words.
Vertical Redundancy Check
(VRC)
- A check
or
par-
ity bit
added
to
each
character
in a message
such
that
the
number
of
bits in
each
character,
including
the
parity
bit,
is
odd
(odd
parity)
or
even (even parity).
Volatile - A
storage
device
whose
contents
may
be
altered
by a
power
shut-off.
The
DV
11
RAM
is a vol-
atile device.
VRC
- Vertical
Redundancy
Check.
WACK
-
Wait-Before-Transmit
Positive
Acknowl-
edgments.
I n Binary
Synchronous
Communications,
this
OLE
sequence
is
sent
by a receiving
station
to
indicate
that
it
is
temporarily
not
ready
to
receive.