User's Manual

SATELLINE-4Pro

User Guide v0.93 DRAFT

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.

10.3 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.

10.3.1 System with several repeaters

In systems with several serial or parallel-chained repeaters, addressing must be used to prevent

messages from ending up in loops otherwise formed by repeaters, and to ensure that only the

desired (addressed) radio modem receives the data intended for it.

All radio modems in the network must be set to a state, in which the RX-addressing is switched ON

and TX-addressing is switched OFF. Base-station and all substations add an address string in the

beginning of the data to be transmitted. In the relaying of the message addressing is used in the

following way:

R1 ADD R2 ADD S ADD

DAT

- The above is the data received from the base station terminal device, containing repeater

addresses (R1 ADD, R2 ADD) and the substation address (S ADD). Two characters define each

address.

R2 ADD S ADD

DAT

- The above is the same message after being relayed from repeater 1 to repeater 2.