Campbell Scientific DC1765 Cellular Telephone Modem - Manual (Page 5)

DC1765 CELLULAR PHONE PACKAGE
3
5. INSTALLATION
FIGURE 5-1. DC1765 Wiring
6. COMMUNICATION USING PC208
Once consistent cellular coverage has been
established on a stationary phone, interference
should not be a problem. Interference on
mobile phones is more easily encountered. The
local cellular company can verify cellular
coverage of a specific area.
When a transceiver moves, the call may be
transferred from one cell to another. Transceivers
generally stay on-line during these transfers, and
data are transmitted properly. However, if all the
cells are busy or if too much interference occurs,
the call will be dropped. This causes the
transceiver and the DC112 to hang up.
Possible sources of interference that should be
avoided include heavy construction sights,
tunnels, transmitting from the fringes of an area,
and power transmission lines.
6.1 TELCOM
TELCOM checks the signature of each block of
data as it is received from the datalogger. A
poor connection will result in the retransmission
of incorrectly received blocks. If a link is
consistently noisy, use of smaller block size
may improve throughput. If the connection is
completely broken TELCOM will record a
"COMMUNICATION BROKEN WITH
DATALOGGER" error message along with the
time and date of the failure in the error (.ERR)
file. TELCOM keeps track of what data was
successfully collected and will attempt to call
the datalogger to collect the remaining data
based on the retry schedule in the station file
was created.
NOTE: If using a relay to switch power to
the transceiver, make sure retries occur at
times the transceiver is on.
6.2 TERM OR GRAPHTERM
If TERM or GraphTerm is being used in the
Monitor or Graph Mode to view datalogger status,
a poor connection will result in "SEQUENTIAL
INTERRUPT" errors. If several successive
SEQUENTIAL INTERRUPTS occur TERM aborts
monitoring and returns to the Option Menu. This
indicates that the connection is either completely
broken or very poor. If the connection is broken, it
is necessary to call the datalogger again before
monitoring can resume. If communication is poor
or interrupted while downloading a program, the
user should verify that the program was received
correctly and that the datalogger is correctly
logging data.