Cal Amp VIPER SC+ 100 series User Manual - page 23
Viper SC+™ IP Router for Licensed Spectrum PN 001-5008-000 Rev. C
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2.1.3. REPORT BY EXCEPTION CONFIGURATION
In a true Report by Exception configuration, the remotes send data to the master only when an event or exception has
occurred in the remote. However, most Report by Exception systems have a master/remote polling component. The
master polls the remotes once every hour or half-hour to ensure there is still a valid communication path. In a Report
by Exception configuration, there will not be a master controlling RF traffic and RF collisions will often occur.
Viper has several collision avoidance features to help minimize collisions. Viper is a “polite radio”. This means Viper will
check the RF traffic on the receive channel before transmitting. If there is no RF traffic present (no carrier present) it
will transmit. If there is RF traffic (carrier present) the Viper SC will buffer the data. Viper will transmit the buffered
data when there is no RF traffic present.
2.1.4. EXTENDING THE COVERAGE AREA WITH A RELAY POINT
A Viper can be configured as a Relay Point (see the following figure). Relay Points provide store and forward repeating
of necessary information from one coverage area to the next. In Bridge mode all traffic is forwarded. In Router mode,
only Broadcast Packets and address specific packets are forwarded. There may be multiple Relay Points to extend
coverage over several hops.
Note: Multiple relay points in a single network may slow the flow of data traffic.
Serial data is always sent out as a broadcast message. A broadcast message cannot take advantage of IP routing mode
so it must use relay points to move from one RF coverage area to another. However, it may be possible to configure
the Viper SC+ so that it may be able to take advantage of the router mode feature and collision avoidance features of
the router mode.
An option to configure the Viper SC+ as a relay point is in the first step of the Viper Setup Wizard or later in the RF
Network tab of the RF Network Settings page. Instructions for completing the Viper Setup Wizard and for configuration
options in the Viper Web Interface tabbed pages are provided later in this User Manual.
Figure 6 – Extending coverage areas by configuring the Viper SC+ as a relay point