Elenco Basic Electronic Experiments - Manual (Page 67)

67
EXPERIMENT #50: LOGIC COMBINATION
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 circuit, test all eight input combinations, and see if you were right.
LED LED
X Y Z Predicted 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
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.
Congratulations! You’ve finished all the experiments and can now show your friends how much you know about electronics!
You are now ready to move on to the next level of Elenco Electronics’ Learning Series. You can also learn how to solder
using Elenco’s line of quality soldering kits! Check out our website (http://www.elenco.com) or see the back cover of this
booklet for how to contact us to order these products.
+9V
100k Ω
3.3k
Ω
WIRE X
WIRE Y
WIRE Z
10k Ω 33k Ω