The SAFE RLI
is a plug-compatible interface replacement for modem
cards 900307 and 900181, used on the DCP-200 and
KDR-1000, manufactured by Thorn Automated Systems,
Inc.
It is packaged as a dual board set. Its purpose
is to convert the DCP or KDR into a device that will
respond to RIM protocol at 300 or 1200 baud over a
20ma loop (with redundant line capability) instead of
the DCP protocol and FSK modems.
The RLI uses one RIM address for every two DCP codes
in a cabinet. That is, an RLI reports 32 inputs per
RIM address (which is equal to two DCP's.) The RLI
monitors up to 4 RIM addresses (which is 8 DCP's -
the maximum in a KDR-1000.).
Additionally, each input point can be inhibited from
the KDS computer by activating the associated RIM
output point.
The RLI continuously
monitors the integrity of the incoming loops. If one
of the loops between the RLI and the KDS is/becomes
defective, then the RLI will send an alarm to the
KDS, to indicate this. There are three alarm
conditions for each loop. A "line fail"
message is sent if a loop is open or shorted. A
"no communication" message is sent if no
data has been received in 4.5 minutes. A "line
noise" message is sent every time 250 errors are
detected. (The RLI statistically analyzes the quality
of data received on each loop and informs the KDS if
excess errors (250) are detected.) By computer output
command, this can be changed to every time five
errors are detected. The RLI samples both lines. A
"no communication," or "line
fail" condition causes the RLI to automatically
switch to the good loop.
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