User's Manual

4-7
Relay Installation
Relay Stations are connected to the Base by twisted-pair wire. See Appendix B:
Adding Relays for the pin outs and a testing plan.
Dealing with radio traffic contention
Radio traffic contention is the other most common hardware related problem you
may have. If tested and configured properly, a single RF Terminal operating with
a single Base Station should be no problem. Regardless of how frequent the
scanning or data entry, radio signal contention is not a serious problem with two
terminals per base. But if you have multiple terminals on a Base and two terminals
happen to transmit exactly at the same time, a collision will occur and neither
transmission will get through to the Base without automatic re-transmission and
associated delays.
Operating with multiple terminals on one Base station increases the chance for
delays due to radio signal contention. A typical RF Terminal application consists
of scanning or data entry followed by movement (i.e. going to another area) or
manual activity (i.e. loading items in a truck) lasting several seconds. This
means there is usually several seconds between each data transmission on a
Terminal. The number of seconds between data transmissions on a Terminal
determines the number of Terminals that can share the same frequency without
significant delays.
The following chart outlines the number of terminals possible on a Base Station
based upon the “average” transaction rate: (this chart assumes a firmware
version of RFx9077J or higher)
Average number of seconds
between transactions on a single
Terminal
Number of Terminals possible on
same frequency/Base
1 2
2 4
3 6
4 8
5 10
6 12
7 14
8 16
Be very careful when coming up with an “average” time between transactions.
You should always use an average based upon your peak activity time. For
example, let’s say that your business operates from 7 am to 5 p.m. Your RF
Terminal operators start scanning at about 7:00, working continuously,
averaging 3 seconds between transactions until 10:00, when operators begin
taking breaks or moving on to work on other projects. Scanning is slow until
5:00, averaging 16 seconds between transactions. If you take an average over the