Operating instructions

1892 1335 - Orion Radio Modem Operating Instructions - v2.9 / Aug 2009 11
v One unit polls the other, volunteering its inputs, and the other replies with its
inputs. Each then mimics the other’s inputs on its outputs.
In either of these arrangements, alarms are sent spontaneously under predefined conditions
unless suppressed, and are acknowledged by the other unit. See page 16.
It is also possible to run a one-to-all topology in this mode, where the Base unit broadcasts its
inputs regularly, and all other units duplicate them on their outputs. This results in a one-way
telemetry link, although two-way User Data is still possible among the units.
v Alarm transmission must be suppressed at the Outstations since the Base is
unable to output them.
v When a broadcast is made, no acknowledgements are returned by the
Outstations nor expected by the Base.
Figure 4 illustrates the two polled arrangements.
Figure 4 - One-to-one and Broadcast polling in Mode I
Frequency of polling can be set over a wide range, from 100ms up to just over a week.
The over-air protocol is fixed and used for both User Data and telemetry.
If a unit expects a response and fails to get it, it can transmit an alarm message, operate alert
contacts, and set its outputs to predefined failsafe values. See page 16.
These topologies are achieved by setting unit addresses to the correct values. See page 14.