SOLUTION:
- Stare at the circuit in terror
- Get a grip; begin coping. Unless you're C Scott, in which case
suffer some more first.
- Realise the circuit's divided into five sections:
- Timing logic (first chunk; resistor ladder feeding
gates and comparators)
- Suspiciously audio-like output stage (mixer, output
driver)
- RF component (fixed tuning)
- Hairy digital logic
- possibly vco like circuit
- Begin circuit analysis, hopefully ignoring details of
timing and output stages for now.
- RF part: realise antenna is tuned to NIST broadcast. Look
it up on google. Find that it broadcasts 440 hz. Realise
this is an "A".
- VCO part: realise the two current sources fight each other as
triggered by the comparator to produce a sawtooth wave at times 3, 4, 6
(see below). Do analysis on cap values and current sources to determine
frequencies which are E and F (or at least their associated frequencies;
if you've seen the suspicious 440hz, hopefully get the pitches, again
from google). Note that Vbe is .6V at the level of current drawn by the
circuit; this can be obtained by checking the datasheet.
- Digital part: discover crystal is an oscillator at 4.9152 mhz.
Discover basic unit is a JK flip-flop, and that the two paths through
the logic frequency divide the oscillator by 2^13 and by 9600, yielding
frequencies 512 and 600hz, which are closest to C and D. (Use flavortext
to ignore accidentals.)
- Figure out the notes, in order, are: A C D E E D F
- Figure out flavortext of taking six steps forward means raise
six half steps, yielding E G A B B A C
- Figure out flavortext of flipping the diagram means reverse,
yielding CABBAGE
- Notice that this puzzle is about groceries. Be happy with the
answer.
0 1 2 3 4 5 6
C A B B A G E
E G A B B A C
Eb Gb Ab Bb Bb Ab B
D F G A A G Bb
Db E Gb Ab Ab Gb A
C Eb F G G F Ab
B D E Gb Gb E G
Bb Db Eb F F Eb Gb
A C D E E D F