Tait TB9100, Installation And Operation Manual

Page: 22 / 144

22 Description TB9100 Installation and Operation Manual
© Tait Electronics Limited May 2006
Signal Voting and Switching
The TB9100 base station receives signals at its four interfaces: RF, analog
line, digital line and control panel microphone. The signals travel along a
path and are presented at the internal voter, as shown in
Figure 1.6 . Often,
the paths for analog FM and for digital P25 signals diverge.
When more than one signal is present, the voter selects the most appropriate
one. Calls made from the control panel microphone are given priority,
followed by signals received at the analog line. Signals received at the RF and
digital interfaces are voted between on the basis of signal quality. Note that
P25 digital signals take priority over analog signals.
When the base station is part of a channel group, the voters in the other base
stations act in concert, selecting the same signal. The switching system then
sends the winning signal to the intended interfaces for transmission.
The channel group can operate in simplex or duplex modes. This mode is
distinct from (but related to) the RF simplex/duplex mode.
Simplex mode
The simplex channel group has a single voter at each channel group
member, which selects one stream from all possible sources, and sends it to
all output interfaces. The vote winner could be a terminal speaker, or a line
interface speaker (dispatcher).
Duplex mode The duplex channel group allows two directions of speech flow
simultaneously. Channel group members vote incoming RF streams and
select one vote winner. The channel group members send this inbound
stream to all line interfaces and control panel speakers (if so enabled). At the
same time, in each channel group member, a separate voter selects one voice
stream from the line interfaces (and control panels), and the outbound
Figure 1.6 TB9100 signal paths
Voter/
Switch
RF
Interface
Control
Panel
Analog
Line
Digital
Line