CAUTION
If
the
terminal
is
to
be
operated in
conjunction
with
a data phone
or
data modem, special care
should
be
taken
to
ensure
that
the interfaces
are per
EIA
Specification RS232C. The logic
levels called
out
in this specification may
cause
serious damage
to
communication inter-
faces designed
strictly
for
standard
DTL
or
TTL
integrated
circuit
logic levels. The
same
precaution should
be
made
when connecting
hard wire
to
any communications 1/0.
Frame Ground
(AA)
This conductor, where used,
is
elec-
trically
bonded
to
the machine frame.
Transmitted Data (BA)
This
circuit
transfers data
from
the
terminal ro the data
set
for
transmission
to
the external device. The terminal holds cir-
cuit
BA
in the mark
condition
during any-
time
interval between characters
or
words,
or
when no signals
are
to
be
transmitted.
Received Data (BB)
This
circuit
transfers data
from
the
data
set
to
the terminal. Signals on this
circuit
are generated by the data
set
in re-
sponse
to
data signals received
from
the ex-
ternal device. The data
set
holds this line
in the mark
condition
when the line
is
idle
or
the carrier
is
not
detected.
Request To Send (CA)
Signals on this
circuit
are
generated
by the terminal
to
condition
the local data
set
to
transmit. The
"on"
condition
is
main-
tained whenever the terminal
has
information
ready
for
transmission
or
being transmitted.
The terminal transmits data on
circuit
BA
(Transmitted Data)
only
when the
"on"
condition
is
maintained on circuits
CA,
CB
and CD. In half-duplex service, the
"off"
3-4
conditions holds data set in the Receive
Data
condition,
and the
"on"
condition
holds the data
set
in the Transmit Data
condition.
Clear To send (CB)
Signals on this
circuit
are generated
by the data
set
to
indicate
that
it
is
pre-
pared
to
transmit
data. The
"on"
condition
on
circuit
CA (Request
to
Send)
is
delayed
as
long
as
may
be
required
to
establish a
connection
to
a external device. When
circuit
CA
is
turned
off,
circuit
CB
is
also
turned
off.
Signal Ground (AB)
This conductor established the com-
mon ground reference
for
all interface lines.
Terminal Ready (CD)
Terminal Ready
is
high whenever
power
is
on.
Received Line Signal Detector (CF)
The signal on this line indicates
that
the data set
has
established the carrier and
the data
set
is
about
to
input
data
to
the .
terminal.
Transmitter Signal Element
Timing
(DB)
Signals on this
circuit
are
used
to
pro-
vide the data terminal
with
signal
transmit
element
timing
information.
Receiver Signal Element Timing (DD)
Signals on this
circuit
are
used
to
pro-
vide the data terminal
with
received signal
element
timing
information.
3.5.4 Printer Interface Connections
Printer interface connections are listed
in Table 3-2.
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