SOUTHERN AVIONICS COMPANYModel SA100 Dual 2-5Theory of Operation, Radiobeacon2.2 Functional Description: Autotransfer System SASeriesThe SAC Radiobeacon Control Systems is composed of a Local Radiobeacon Control Panel andone or more optional Remote Control Panels.Primary AC power and auxiliary battery power is attached to terminal blocks on the LocalRadiobeacon Control Panel relay assembly. The Relay Assembly in the SA Local RadiobeaconControl Unit is Relay PWB SLP05004 which is installed within the LRCU-SSC cabinet. Power isrouted through relays within the relay assembly to Transmitters 1 and Transmitters 2. RF fromthe transmitters is routed through the relay assembly to the antenna coupler.Logic signals generated in the monitoring circuits of each of the two transmitters are routedthrough the relay assembly and Local Control Motherboard to the Transfer Logic PWBSLP09904/06. Control signals are routed from the Transfer Logic PWB through the Local ControlMotherboard to the Relay Assembly Control relays.The minimum configuration of the Radiobeacon Control system is a Local Radiobeacon ControlPanel composed of an Autotransfer Logic PWB, Local Control Motherboard, Transfer IndicatorPWB SLP24730 and a Relay Assembly package. This configuration enables control of thetransmitter through the Local Radiobeacon Control Panel only. The power switch located on theLocal Radiobeacon Control Panel acts as the primary power switch for the transmitter system bysupplying power to the Local Radiobeacon Control Panel. This switch must be ON to enablelocal and remote control of the transmitter system. With the power applied to the LocalRadiobeacon Control Panel, the Autotransfer Logic Board in conjunction with the front PanelTransfer Indicator Board controls the power, transfer, and status indications for each of the tworadiobeacon transmitters. Latching relays located on the Local Control Motherboard retain thelast control states supplied to the Autotransfer Logic Board from the control panel switches.Shutdown indications are supplied to the Autotransfer Logic Board from the monitoring circuitswithin each of the transmitters.Control voltages are supplied from the Autotransfer Logic Board to the Relay Assembly to switchpower relays controlling DC and AC power to each of the two transmitters and to control theposition of the antenna transfer relay.Optional printed wiring board connectors are installed on the Local Control Motherboard toenable future expansion of the Radiobeacon Control System to full remote control.Remote control of the radiobeacon is accomplished by installation of the Serial Interface Boardand a Modem Board in the appropriate Local Control Motherboard Connectors and installing aRemote Radiobeacon Control Panel at the selected remote control site. An audio control linkcapable of full duplex 300 baud FSK communications is installed between the local and remotesites. If required, a second remote control panel can be installed with communications over 4wire shielded line between this panel and the local panel.A Standby Test mode is available for testing and repairing the secondary transmitter while theprimary transmitter is operating normally. Placing the standby test switch in TEST applies powerto the secondary transmitter. NOTE THAT A 50 OHM LOAD SHOULD BE CONNECTED TOTHE DUMMY LOAD OUTPUT IN THE LOCAL RADIOBEACON CONTROL UNIT. When theswitch is in the TEST position, automatic transfer is inhibited. If either transmitter shuts down, notransfer will occur.
