42 Functional Description TB8100 Installation and Operation Manual
© Tait Electronics Limited June 2005
base station operation, but is also used for single base station operation
because it provides the I
2
C current source normally provided by the PMU.
Note The dual base station subrack interconnect board has a set of
switches which must be set according to the type of base station
system in the subrack. Refer to “Replacing the Subrack Intercon-
nect Board” on page 98 for details of the switch settings.
Power Saving operation in a 12V PA base station requires an external
connection between the reciter and 12V PA (refer to “12V PA Power
Saving Control Connection” on page 124). For details on Power Saving in
a 12V PA base station, refer to “12V PA Operation” on page 60.
Constraints The dual base station control panel imposes the same constraints on the
operation of a dual 12V PA BSS as those described in “Service Kit” on
page 40, except that those which refer to the PMU do not apply.
In addition, because there is no PMU fitted, we recommend the following
Service Kit settings for 12V PA base station operation:
■ Disable the “No PMU detected” alarm on base stations 1 and 2.
4.2 System Control Bus
The system control bus, see Figure 4.4 on page 44, provides the
communications link between the modules in the TB8100 BSS. It provides
the following physical paths:
■ I
2
C communications between modules
■ RS-232 communications between the reciter and Service Kit and
Calibration Kit software, via the control panel port
■ fan power from the PA and PMU
■ speaker and microphone signals to and from the control panel
■ power connections for the control panel.
The system control bus has been designed so that, if a major fault occurs on
the bus, the basic operation of the base station is unaffected, but some
features will not operate correctly. For example, if the PA is disconnected
from the bus:
■ the ‘PA not detected’ alarm is generated in the reciter; however,
transmission still takes place because the transmit RF and key signals are
transmitted from the reciter to the PA via the interconnecting coaxial
cable
■ the PA is unable to turn on its fan. Depending on the ambient
temperature at the site and the transmit duty cycle, this could allow the
PA to heat up to the point where it reaches the upper temperature
threshold. At this point it will begin power foldback, protecting the
equipment from damage.
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