Input Output A 0 0 1 1 B 0 1 0 1 1 0 0 0 Input Output A 0 0 1 1 B 0 1 0 1 1 1 1 0 The Negative AND  gate The Negative OR  gate Input$_{A}$ Input$_{B}$ Output Input$_{A}$ Input$_{B}$ Output A. B. N-S E-W XPDR 5537 IDNT LCL23:00:34 VOR 1 270 ° 2 1 1 2 4 300 4 200 4 100 4 000 3 900 3 800 4300 3600 3500 3400 3300 3200 3100 60 20 000 130 120 110 90 80 70 1 100 9 TAS 100KT OAT 7°C NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1 123.800 118.000 COM2 $_{WPT }$_ _ _ _ _ _$_{ DIS }$_ _ ._ $_{NM}$ $_{DTK }$_ _ _$_{°}$ TRK 360° XPDR 5537 IDNT LCL23:00:34 VOR 1 270 ° 2 1 1 2 4 300 4 200 4 100 4 000 3 900 3 800 4300 3600 3500 3400 3300 3200 3100 60 20 000 130 120 110 90 80 70 1 100 9 TAS 100KT OAT 7°C NAV1 108.00 113.00 NAV2 108.00 110.60 134.000 118.000 COM1 123.800 118.000 COM2 $_{WPT }$_ _ _ _ _ _$_{ DIS }$_ _ ._ $_{NM}$ $_{DTK }$_ _ _$_{°}$ TRK 360° 11-29 Figure 11-70.  A modern glass cockpit on a general aviation aircraft. Digital data displays replace many older instruments and indicators  of the past.  Figure 11-69.  The NEGATIVE AND gate symbol and its truth table  (A) and the NEGATIVE OR gate symbol and truth table (B). The  inputs are inverted in the NEGATIVE gates. Digital Aircraft Systems Digital Data Displays Negative Logic Gates Modern digital data displays are the most visible features  of digital aircraft systems. They extend the functional  advantages of state of the art digital communication and  navigation avionics and other digital aircraft systems via the  use of an enhanced interface with the pilot. The result is an  increase in situational awareness and overall safety of flight.  Digital data displays are the glass of the glass cockpit. They  expand the amount, clarity, and proximity of the information  presented to the pilot.  [Figure 11-70] There are also negative logic gates. The negative OR and the  negative AND gates are gates wherein the inputs are inverted  rather than inverting the output. This creates a unique set of  outputs as seen in the truth tables in  Figure 11-69 . The negative  OR gate is not the same as the NOR gate as is sometimes  misunderstood. Neither is the negative AND gate the same  as the NAND gate. However, as the truth tables reveal, the  output of a negative AND gate is the same as a NOR gate, and  the output of a negative OR gate is the same as a NAND gate. in an EXCLUSIVE OR gate. When either of the inputs is  Logic 1, the output is Logic 1. But, if both inputs are logic  1, the Logic 1 output is excluded or Logic 0.  [Figure 11-68] Digital aircraft systems are the present and future of aviation.  From communication and navigation to engine and flight  controls, increased proliferation of digital technology  increases reliability and performance. Processing, storing,  and transferring vital information for the operation of an  aircraft in digital form provides a usable common language  for monitoring, control, and safety. Integration of information  from different systems is simplified. Self-monitoring, built-in  test equipment (BITE) and air-to-ground data links increase  maintenance efficiency. Digital buss networking allows  aircraft system computers to interact for a coordinated  comprehensive approach to flight operations.  In summary, electronic circuits use transistors to construct  logic gates that produce outputs related to the inputs shown  in the truth tables for each kind of gate. The gates are then  assembled with other components to manipulate data in digital  circuits. The electronic digital signals used are voltage or no  voltage representations of Logic 1 or Logic 0 conditions. By  using a series of voltage output or no voltage output gates,  manipulation, computation, and storage of data takes place. 