User's Manual
ECLIPSE2 IPCommander User Manual
20
5.16. Maximum Deviation
Displays the maximum transmitter deviation for the current channel.
Typical maximum deviation values are 2.5KHz for Narrowband channels and 5KHz for
wideband channels.
5.17. TX VCO
Shows the current TX VCO tuning voltage and PLL frequency.
5.18. TX P25 NAC
Displays the current TX NAC.
Only displayed when the C4FM modulator is present on the signal map.
5.19. Voting
In-base voting is used to determine the base station with the best incoming signal, and to pass the
signal from that base station to other bases.
It is recommended that base stations be part of same IP multicast group.
When the base stations are receiving, they send their RSSI values to each other. One of the base
stations will determine that it has the highest RSSI value, become the master base station and then
inform all the other base stations that they are slaves.
The slave base stations will listen for audio packets from the master base station, for the duration of
the call, until the following conditions arise:
1. The master’s RSSI value falls below -107dbm, in which case a new master base station will
be assigned
2. All the base stations stop receiving, which will invoke a restart of the voting process
3. The master base station stops receiving and a new master is assigned
Base Stations can join or leave the multicast group without causing system failure. (no permanently
assigned master).
This type of voting architecture is distributed, thus no central voting comparator is required.
The Audio packets are sent only from the master to the slaves, the master base station transmitting
its own received audio locally.
The data rate of a stream is approximately 100Kbps using the G711 audio codec, thus only 100kbps
per base station is required.
Comparing the above distributed voting to the use a central voting comparator, for a central
comparator ALL audio packets are routed via the voter for processing. Since there are now separate
receive and transmit audio paths required per base station, the required data rate (and consequently
bandwidth) is doubled to 200kbps per base station.