I
'
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.
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After the
Modem has dialed the number, it forces
carrier detect for
two
seconds
—
then releases
it.
This time period
allows
the
receiver filters
to
stabilize from the
impedance change
presented
by the
phone line. The Modem then
waits for carrier from the
remote modem for
a
period
of
12
seconds. If carrier is detected, the
Modem asserts carrier detect to
the Computer. If carrier is not
detected, the Modem
drops the phone line and, after a three
second delay, executes the front
panel switches.
The
Modem
override
(from
AUTO/ANS to AUTO/ORIG) is
programmed by entering the
programming mode, sending a
number to dial, and
executing by asserting DTR. The Modem
will internally
switch filter banks and
transmit/receive frequencies
under microprocessor control.
It will then act
exactly as if the Modem
was
in
AUTO/ORIG Mode.
After
a
disconnect,
it
will
go
back to
AUTO/ANS Mode. The
override program is still intact as
long
as
power
is applied.
If
further
overrides are necessary, place the Modem
in programming mode and
either re-program
the
phone number or send an X
and assert DTR.
See
Appendix B for a complete
explanation of the Modem
programming codes.
AUTO/ANSwer
Operation
Another unattended
use
of
the Modem II is in an
AUTO/ANSwer
environment. The Modem is
easy
to use in this
mode.
To use the
Modem II in AUTO/ANSwer Mode:
1 . Set the MODE
Switches to:
ja^jsw«--^wteB.
a
'aa.M&n ^wwa.'fe^a tM*a**m *>wru
POWER
2. Assert DTR
(by the
Computer or by
the FORCE
DTR
Switch).
3.
Set the Modem's
POWER
Switch to ON.
The ON
and TR
Lights will go
on.
After the
phone rings, the
Modem
seizes the
line, delays
for two
seconds, and transmits
carrier.
It then
waits 12
seconds for
the remote
modem to
send carrier.
If it does not see the
remote
carrier, it
disconnects from the
phone line,
delays
three seconds,
and goes back to
AUTO/ANSwer
Mode and
waits for
the next
call.
There may
be some
instances
when it
is desirable
to tell the
Modem not to
answer an incoming
call or to
hang up
on a call
in
progress. This is
done by
either turning
FORCE DTR OFF or by
placing
the Modem
in the
LOCal
Test Mode.
This is
only practical
if FORCE DTR is off since
the
only way to
get out of a
LOCal Test
(programmed
by the
Q
command) is to set the
Modem's
FORCE
DTR to
OFF.
The
LOCal Test
resets the
ring detect
circuitry inside the Modem so
incoming
rings
are
ignored.
21
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