Tait TB8100 Installation And Operation Manual

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Tait TB8100 Installation And Operation Manual Manual pdf 56 page image

56 Functional Description TB8100 Installation and Operation Manual© Tait Electronics Limited June 2005The PA and PMU sections on Figure 4.13 show most of the monitoredparameters in each module and the control outputs from themicroprocessors, which are also available to the reciter RISC via the I 2 C busand form the basis of the TB8100 monitored alarms.Each reciter, PA and PMU module also stores the following informationspecific to that module: calibration parameters serial and product number factory configuration.This ensures that the module is a true entity in its own right, thus helpingto support simple ‘plug and play’ site module replacement procedures.The TB8100 control panel provides several important functions.Depending on the control panel version these functions include, but are notlimited to, the following: an interface point to monitor and respond to failure alarm outputs fromthe fans a point to read key presses and display base station status on output LEDs speaker control and amplifier for on-site monitor audio.All control panel logic inputs and outputs are implemented by using an I 2 Cport expander that performs a serial (I 2 C) to parallel conversion (and viceversa) over the I 2 C bus. The control panel port expanders are fixed address8-bit input and output interfaces. The heaviest user of the I 2C bus is actuallythe control panel keypad read polls which occur on average every 50ms.4.7 Fan OperationThe cooling fans are mounted on the front panel. One fan is in front of thePA and another in front of the PMU. The fans do not operate continuouslybut are switched on and off as needed by the reciter firmware. When thebase station is switched on, both fans come on for a short time and are thennormally switched off. The operation of the PA fan is configurable via theService Kit but the PMU fan is not. It has fixed on/off thresholds and adefined set of duty cycles based on the PMU temperature, as follows:PMU Temperature Duty Cycle<65°C (<149°F) Increases with increasing current draw65°C to 75°C (149°F to 167°F) On two minutes, off one minute>75°C (>167°F) Always on