SATEL-EASy+
User Manual
Version 1.19
55
13.2.2
System of one base station and several substations
In systems with several substations, the base station must know to which substation each
message is intended, and from which substation each received message originates. Usually
terminal devices handle addressing completely, but it is also possible to use the addressing
functionality of the radio modems.
For example, if the substation terminal devices are not able to check and form addresses by
themselves, addressing may be achieved with the help of the addresses of the radio modems
attached to these terminal devices. The base station may, in such a case, define the destination
of a message by adding the address of the corresponding radio modem into the beginning of the
data packet. The substation radio modem(s) will check the address and the corresponding radio
modem will identify and remove the address characters. In a similar way, the substation will add
when transmitting to the base station its address characters into the beginning of the data
packet, thus defining the origin of the sent data packet. In the base station radio modem,
addresses have been switched OFF, so that they are transmitted as is to the base station
terminal device for further processing.
13.3
Using repeaters and addresses in the same system
In systems with several repeaters, a substation and a base-station, addresses must be used in
radio modems. It is possible to realise also a system with only one repeater without addressing.
In such a case, the base station will however hear the message both from the substation and
from the repeater, in other words the message is duplicated as it moves along the route.
There are at least two ways of realising such a system depending on the capabilities of the
terminal devices in question and on the number of repeaters to be used and on their relative
positions to each other.