TB7100 Installation and Operation Manual Functional Description 39© Tait Electronics Limited December 2005The SI board provides an unbalanced audio input and output for connectingto other devices.3.4.7 Opto Isolated KeyingExternal keying of the base station can be achieved using the currentregulated optically isolated keying connections.3.4.8 Relay OutputThe SI board can provide a relay output with a load voltage of 350V or loadcurrent of 120mA continuous. The SI board can also provide a relay driveroutput. Both these options are configurable and these settings are discussedin “Preparation for Operation” on page 77.3.4.9 Fan ControlThere are three modes of operation for the fans. The modes are:■ on continuous■ on when transmitting■ on at a pre-defined temperature.The modes of operation are selected by links on the SI board. These settingsare discussed in “Preparation for Operation” on page 77.3.4.10 RSSIA received signal strength indication (RSSI) voltage is developed by thereceiver module and applied directly to the SI board rear panel.3.4.11 Receiver GateThe receiver gate signal is used by the SI board to control TOI and a relayoutput. The receiver gate output on the SYSTEM connector can be used forexternal equipment such as TaitNet trunking controllers.3.4.12 Receiver InhibitThe receiver inhibit input on the SYSTEM connector is used to control thereceiver gate signal. This may be used in linking applications to preventunwanted receiver audio signals from appearing at the SI board outputconnector.
