Electronic Fundamentals and Digital Techniques / Electronic Instrument Systems
Components
Diodes conduct when forward biased (about 0.6–0.7 V for silicon) and block in reverse. Know half-wave, full-wave and bridge rectifiers, the transistor as a switch or amplifier, and the ideal op-amp (infinite open-loop gain and input impedance, zero output impedance). Memorise the truth tables for AND, OR, NOT, NAND, NOR and XOR, and remember that NAND and NOR are the universal gates from which any logic function can be built.
Digital technique
Be able to convert between binary, octal, decimal and hexadecimal, use two's complement for negative numbers, and distinguish bits, bytes and words. Know serial versus parallel data transfer and the aircraft databuses: ARINC 429 is a one-way, 32-bit-word bus running at 12.5 or 100 kbps; ARINC 629 and its Ethernet-derived successors are bidirectional and much faster; MIL-STD-1553 is bidirectional and time-multiplexed.
Instruments
Displays moved from CRT to LCD. EFIS, EICAS/ECAM, FMS and glass cockpits fuse data from air data computers and inertial reference units. Understand the pitot-static group (airspeed indicator, altimeter, vertical speed indicator), gyroscopic instruments, and how an ADC or IRU failure shows as a flag or invalid-data message on the display.
The traps
Confusing decimal, binary and hex; getting XOR backwards (output high only when inputs differ); claiming ARINC 429 is bidirectional (it is not); muddling which source feeds which display.
Worked example
Binary 1011₂ = 8 + 0 + 2 + 1 = 11. Hex 2F = (2 × 16) + 15 = 47. Rule of thumb: group binary digits in fours from the right to convert straight to hex.