Casio PV-750 Plus Technical Reference Manual page 19

Make sure you are inputting the time correctly.
Cause: You are inputting invalid
values for a time setting.
Cause: You are trying to input data
or receive data while memory is
already full.
Cause: The modem could not be
initialized for some reason.
Cause: During connection, host
became busy and failed to respond
further.
Cause:
There is no response from the
phone when sending or receiving SMS
or Phone Book data.
Cause: The time you are trying to
set for an alarm is already passed.
198
Memory is full!
Modem initialization failed.
No response from the host!
Phone is not responding!
That alarm time is already passed!
Action: Input proper values for the
time.
Action: First try performing the
memory management operation to
see if more memory can be made
available. If this message still
appears, it means that memory is
really full. Delete data you no longer
need to make room for more data.
Action: Make sure the mobile phone
is turned on. Also check to make
sure that your mobile phone is set up
for e-mail send and receive.
Action: Tap OK to clear the error
message. Change to another access
point or try again later.
Action:
Tap OK to clear the error
message. Make sure that the infared
ports of your PV unit and of your mobile
phone are facing directly at each other.
Action: This is merely a warning
message that appears for about one
second. After that, the dialog box
closes and the data is stored without
the alarm.