Elenco Electronic Playground 50-in-1 Experiments - Manual (Page 70)

-70-
This last circuit is a combination of some of the other
digital gates, and has 3 inputs. See if you can fill in the
truth table by just looking at the schematic. Then connect
the wires according to the Wiring Checklist, test all eight
input combinations, and see if you were right. What could this circuit be used for? It might be used to
provide power for your telephones. Z would be controlled
by the phone company and would be high if you paid your
phone bill. X and Y could be different phones in your
house and would be high when you pick up the phone.
The transistor emitters would then provide voltage to the
rest of the telephone circuit.
EXPERIMENT #51: Logic Combination
Wiring Checklist:
o 17-to-20-to-26
o 16-to-19-to-14
o 13-to-2
o 1-to-42
o 15-to-44
o 45-to-unconnected (this is
referred to as wire X)
o 18-to-46
o 47-to-unconnected (this is
referred to as wire Y)
o 12-to-51
o 52-to-unconnected (this is
referred to as wire Z)
o 43-to-27
Schematic
Wire X
X Y Z LED 1
Predicted
LED 1
Measured
LOW LOW LOW
LOW LOW HIGH
LOW HIGH LOW
LOW HIGH HIGH
HIGH LOW LOW
HIGH LOW HIGH
HIGH HIGH LOW
HIGH HIGH HIGH
Wire Y
Congratulations! You’ve finished
all the experiments and can now
show your friends how much you
know about electronics! What to
do next? Well, you can re-do your
favorite experiments or look our
list of other Elenco
® Electronics
learning products!
Wire Z