EFFECTIVITY
IB ALL CONFIG 3 01 Page 9 Dec 25/8734-53-00
(11) Altitude reporting may be initiated in mode A, or B if the ALT REPORT switch is in the ALT REPORT position. Altitude reporting is initiated upon the reception of a 21-microsecond interrogation pulse pair from the ground station. During altitude reporting, digital altitude data from the CADC is applied to the gate in the ATC transponder. The position (1 or 2) of the ATC switch on the ATC control module determines whether altitude data from CADC 1 or CADC
is utilized by the ATC system. (12) The operational status of the two ATC transponders is controlled by the function selector and the ATC switch on the ATC control module.
XA When the
XA XA XA function selector is set to STBY the power supply provides power to all circuits in both transponders. The ATC system is placed in operation by setting the function selector to A or B. The turn-onsignal is applied to the control matrix of either ATC 1 or ATCtransponders as determined by the position of the ATC switch.
XA
(13) Switching of altitude data from either of the two central air data computers (CADC) to the ATC system is illustrated in figure 4. Twelve altitude encoding electronic switches within each CADC altitude encoder are opened or closed in accordance with the coded digital equivalent of the airplane altitude. A flag switch within the CADC is closed whenever the altitude data is valid and the CADC
is operating normally. With the ATC switch on the ATC control module set to position 1, current flows through the ATC switch, through the flag switch, and through any of the altitude encoding switches that are closed to cause a voltage drop across the corresponding resistors in ATC 1 transponder gate. The digital altitude code is picked off of the twelve resistors and encoded by the gate for transmission to the ground station. With the ATC switch in position 1, therefore, ATC 1 receives altitude data from CADC 1. Likewise, with the ATC switch in position 2, ATC 2 receives altitude data from CADC 2.
XA XA XA XA XA XA XA XA XA XA XA XA XA XA XA XA XA (14) Action on the self test button of the Control bus or of thetransponder front panel permits a rapid check of the operationalstatus of the transponder. The self test oscillator, controlledby the control matrix delivers an interrogation signal to thepreselector. If no fault exist a reply is generated.(15) The control box contains a fault light and a reply light. Thetransponder front panel contains a reply light included in the selftest switch and two fault indicators (R/T and ANT). The monitorcircuit supplies signal to these to provide indication of theoperational status of the equipment. When four consecutive repliesare completed the reply lights are momentory energized. If afault occurs, the fault lights on the control box and one of thetwo indicators on the transponder front panel are energized thefault lights will remain for 15 seconds longer than the faultcondition exists. The ANT fault indicators on the transponder isreset by depressing the reset switch on the front panel. The R/Tindicators is reset by grounding a terminal inside the unit.
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