Operation
RFI-9256 Radio Modem User Manual
Page 30 of 109
RFI-9256
Master 1
HPSN=0
Addr=1000
RFI-9256
Slave 1
HPSN=0
Addr=20
RFI-9256
Master 2
HPSN=1
Addr=20
RFI-9256
Slave 2
HPSN=1
Addr=3000
Wiring
Harness
Figure 11: Back-to-back repeater configuration
A back-to-back repeater configuration is the joining two separate RFI-9256 networks via a wiring harness
between a slave on one network and the master of a second network. The wiring harness can link the main
port, auxiliary port, or both ports via a null-modem cable. A wiring diagram for a back-to-back repeater
cable that links both main, auxiliary, and the auxiliary I/O lines is given in Appendix A.5 on page 62.
When setting up back-to-back repeaters, the following rules should be followed:
Both master and slave radio must have the same local address, and it must be in the range 10-99
(i.e., two characters).
All other radios in the network must have local addresses in the range 1000-9999.
These rules come about due to the way Hayes dial-up works in a back-to-back repeater network. See section
5.3.3 on page 34 for more information on Hayes dial-up networking.
Back-to-back repeaters should be synchronised, as discussed in the section Synchronisation on page 28, in
order to prevent them from jamming each other due to collocated antennas.
The slave must be configured to output a synchronisation signal.
The master must be configured to follow a repeater synchronisation signal.
This guarantees that both master and slave will transmit at the same time.
5.2.4 Performance Tuning
LATENCY REDUCTION
Some systems will require a radio link that induces very low latency, usually where the RFI-9256 is being
used to replace an existing wired system. There are a number of parameters that can be traded off in order to
reduce latency.
Throughput:
The throughput of the RFI-9256 can be reduced, with a corresponding reduction in
latency. This is achieved by reducing the frame time as the frame time has a direct impact on
latency. A smaller frame time will give lower latency. See section Latency on page 24 for a more
information.
