User`s manual

CR-SEH
used to distinguish between networks of CR-SEHs and to prevent interference between the CR-SEH
networks.
If the master CR-SEHs are not located close to each other (> 30 feet or 10 meters apart), simply assigning
different network numbers to the various networks of CR-SEHs will allow the networks to co-exist
without interference. The network number selects one of 63 different hopping patterns, where the hopping
pattern is the pseudo-random sequence of frequencies over which the CR-SEHs hop. Because the
different networks are using different sequences they will transmit on the same frequency at the same
time only rarely. These infrequent collisions are not sufficient to reduce the throughput in any meaningful
way.
If the master CR-SEHs are to be located close together, the CR-SEHs allow the masters to be
synchronized as to when they send to slaves and when they receive from slaves. This synchronization is
allowed by the FCC in the United States. The FCC does not allow synchronizing of the hop sequences to
avoid all collisions. The CR-SEH accomplishes the send/receive synchronization through use of the Sync
ports. The Sync ports of the CR-SEH masters are connected using standard RJ-11 cables. There is a Sync
In and a Sync Out port to allow daisy-chaining of CR-SEH masters. One of the CR-SEH masters is
designated the Sync Master using the
sync master command. Synchronization is enabled in the Sync
Master and all connected master CR-SEHs using the
sync enable command. The sync wire
command must be issued to turn on the Sync ports. Refer to the Radio Commands section for details.
Note: When synchronization is used in the United States, the hop fcc parameter must be
left enabled. Disabling this parameter will violate FCC rules governing spread spectrum
radios.
 2000- 2004 Cirronet Inc 18 M-2411-0013 Rev A