User's Manual

ISO 9001:2000 Cert. N°4500/1
Version 1.1 SDT_ARK6_User_Manual_ENG_vATSC Page 195 of 206
Feed selection and switching criteria are available via both transmitter SNMP and Java GUI interfaces.
A Finite State Machine has been used to give a description of the behaviour of the system. The FSM of the Input
Autoswitch algorithm consists of:
 Four states:
1. Priority Input Locked
 Condition: the primary feed is the one being used.
2. Priority Input Not Locked
 Condition 1: the primary feed does not meet the necessary quality requirements as
well as reserve feeds, if any.
 Condition 2: the primary feed does not meet the necessary quality requirements and
the FSM is waiting for the primary to secondary feed changeover timeout to elapse.
3. Searching First Locked Input
 Condition 1: the primary to secondary feed changeover timeout elapsed and the FSM
is searching for a reserve feed.
 Condition 2: the reserve feed, the one being used, does not meet anymore the
necessary quality requirements, the secondary to secondary input switch timeout
elapsed and FSM is searching for another reserve feed.
4. Checking Priority Input
 Condition: the reserve input is the one being used and FSM keeps checking the priority
feed to trigger the secondary to primary changeover.
 Three countdowns to N seconds, where N is defined by default in the *.def file:
1. Primary to Secondary Switch Counter
 It starts when the primary feed does not meet anymore the necessary quality
requirements and the system lay in waiting for the reserve feed to be checked.
2. Secondary to Secondary Switch Counter
 It starts when the secondary feed does not meet anymore the necessary quality
requirements and the system lay in waiting for another reserve feed to be checked.
3. Secondary to Primary Switch Counter
 It starts when the input set to priority is found to meet again the necessary quality
requirements and the system is waiting to switch back to the primary input.
Timeouts are reset when the actually used input, whether it is the preferred one or not, regain his quality
requirements.