Radio Shack TRS-80 Model III

TRS-80
MODEL
III
Clear-
to-Send:
Direction-from
data
communication
equipment.
This
signal
is
generated
by the data
communication
equipment
and indicates
whether
or
not the
data
set
(modem)
is
ready
to transmit
data.
The
"on" condition
is
an indication
to
the data
terminal
equipment
that
the data
set can
accept data
on the
Transmit
Data
circuit.
The
"off
'
condition
is
an indication
to the data
terminal
equipment
that
it
should
not
transfer
data
to the data
set
.
Data Set
Ready:
Direction-from
data
communication
equipment.
This
signal
indicates
the
status of
the local
data
set to the
data terminal
equipment.
The
"on'
'
condition
of this
circuit
indicates
that
the data
communication
equipment is
not in
test,
talk
or dial
mode
and has
completed
any timing
functions
required
to complete
call
establishment
(answer
tone
,
etc
.
)
.
The
"off '
condition
will
appear
at all
other
times
and
indicates
that
the
data
terminal
should
accept
only Ring
Indicator
signals
and ignore
all
other signals
(appearing
on
any
other
interchange
circuit).
Data
Terminal
Ready:
Direction-to
data
communication
equipment.
This
signal
is
used
to
control
the switching
of the
data
communication
equipment
to the
communications
channel
.
The
"on"
condition
indicates
to data
communication
equipment
that it
should
connect
to the
communications
channel
and that
it should
maintain
the
connection
as
long
as the
"on"
condition
is
present. The
'
'off
'
condition
causes
the data
communication
equipment
to
be removed
from
the
communications
channel
following
any
in-process
transmission
of data.
Ring
Indicator:
Direction-from
communication
equipment. The
"on"
condition
of
the
circuit
indicates
that
a
ringing signal
is
being received
on the
communications
channel
.
In general
,
this
means
that
the data
set is being
polled
and
that
data
communication
is
desired
by the polling
device.
The
"off
'
condition
is
held
during
the off
segment
of the
ringing
cycle
(between actual
rings)
and
at all other
times
when
ringing is
not
being
received
.
Carrier
Detect
(Receive
Line
Signal Detector):
Direction-from
data
communication
equipment
.
When
"
on
"
, this signal
indicates
that the
data
set
is
receiving
a
carrier from
a remote
data set via
the
communications
channel
. The
'
'off
'
condition
indicates
that no
carrier is
being
received
or that
the
signal
quality
is
unsuitable
for data
demodulation.
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