3-1
Chapter 3
Operational Theory
Before you jump in and start writing a complex host program, it might be nice to
be familiar with the theory behind the operation of your RF Terminal. The RF
Terminal has three different modes of communication:
•
Two-Way Mode
- the host program transmits requests for data to
the terminal via the Base Station. The RF Terminal transmits a
response back to the Base Station, which in turn sends the data on to
the host program. This is a truly interactive mode allowing you to
create flexible programs for a variety of applications that are
computer led and controlled.
•
One-Way Mode
- the RF Terminal transmits to the host with only
confirmation from the Base Station. The host program receives data
from the Base Station as it would any other serial device. The host
cannot send data to the terminal; it can only receive information.
•
Site Test Mode –
the Base Station and RF Terminal work together to
evaluate the site and determine the best location for the Base Station.
The site test evaluates the percentage of successful transmissions on
the first and second tries from any given area. The higher the
percentage, the more successful your communications will be from
that area. This helps you to identify problem areas before you
implement your RF Terminal system. At 30 ft., this is also the acid
test for suspected bad radios in a base or in a terminal.
Let’s start with a discussion of the basic theory behind a
Two-Way
RF Terminal
system.
How the Two-Way RF System works
Basic RF System communications…
The RF system consists of three components –
Host Computer
,
Base Station
and
RF Terminal
. The
Base Station
connects to the
Host Computer
via the
serial port. The application running on the
Host Computer
sends a data
prompt to the serial port where the Base Station receives it. The
Base
Station
then transmits the data prompt via radio frequency to the intended
RF Terminal
. The
RF Terminal
displays the data prompt on the display and
waits for the operator to enter the requested data. Once the operator enters
his data, the
RF Terminal
transmits the data to the
Base Station,
which in
turn passes it on to the
Host Computer
. The application on the host com-
puter processes the information and sends a new data prompt out to the
Base Station
and the whole process begins again.
