Macintosh Communications
261
the modem lists the various settings for the
Dual
In line Package
(DIP)
switches which
are
located behind the modem's front
panel. Adjust these settings as they pertain
to
your needs.
To
activate the Hayes modem, locate the small toggle switch in the
back
of
the modem. Flip it
to
the
up
or
"on"
position,
and
the
modem's
LED
display lights should shine. These lights indicate
the following conditions:
• M R - Modem ready
• TR - Terminal ready
•
SO
- Send data
•
RD-
Receive data
•
OH-
Off hook condition
•
CD-
Carrier detected
• AA - Auto answer mode
The M R lamp is always lit when the modem
is
turned on.
If
it is
not
lit, either the lamp is
burned
out,
or
the modem is not
functioning properly. The
TR
lamp is normally always lit
except
under
special conditions which are described in the
operations manual for the modem.
The
SD
and
RD
lamps indicate similar conditions. They
light whenever the modem
is
sending (SD)
or
receiving
(RD)
data. These lamps become
important
when you wish to moni-
tor
the
data
transfer process.
When making
or
receiving a call, the modem must set the
telephone in the
off
hook
condition. You
do
this manually
whenever you lift the telephone receiver. When the modem sets
the phone to the off
hook
condition, the 0 H lamp will light.
When the
modem
makes a communications link with
another
modem,
it
sends a
constant
signal
through
the tele-
phone line. The opposing modem does the same. This constant
signal is called a carrier. When the modem receives the carrier
from the
other
side, the
CD
lamp
will light indicating
that
a
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