Elenco Electronic Playground 50-in-1 Experiments - Manual (Page 69)

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Using the LEDs for these truth tables probably seems a
little boring. So let’s use an audio circuit to make a sound
instead of turning on the LED. Connect the wires
according to the Wiring Checklist. Can you tell which
digital gate this circuit represents? Construct the truth
table to find out.
It is the NAND gate. If you use longer wires for X and Y
and leave them connected HIGH then you have an alarm
with two separate trip wires.
You can easily modify the circuit to be an AND gate.
Remove the 3.3K
Ω resistor and 10μF capacitor, connect
spring 24 (transformer) to spring 27 (battery) instead of
spring 16 (NPN1 collector), and connect spring 14 (NPN3
emitter) to spring 16 (NPN1 collector) instead of spring
20 (NPN2 emitter). This audio circuit can also be used
with the OR and NOR gates simply by rewiring NPN1,
NPN2, and the 10K
Ω, 33KΩ resistors.
EXPERIMENT #50: Audio AND, NAND
Wiring Checklist:
o 14-to-20-to-26
o 17-to-19
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-32-to-51
o 5-to-21
o 6-to-22
o 13-to-23
o 33-to-52-to-25
o 24-to-16-to-42-to-35
o 34-to-43-to-27
Wire X
Wire Y
Schematic