Elenco Upgrade Kit SC300 to SC750 - Manual (Page 23)

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Project #353
OBJECTIVE: To make a relay buzzer.
When you turn on the switch (S1), you should hear a buzzing sound
from the relay (S3). The sound is caused by the relay’s contacts
opening and closing at a fast rate.
Relay Buzzer
Project #352
OBJECTIVE: Light a bulb using a relay.
Bulb & Relay
Turn off the slide switch (S1). If you press switch (S2), the lamp (L2)
will not light. Turn on the slide switch and press the press switch again;
the lamp lights and stays on until the slide switch is turned off. This
circuit remembers that the press switch was pressed. Turn the slide
switch off and back on again. The lamp will be off until the press switch
is pressed, then the lamp will stay on. Computers use memory circuits
to remember states like on and off.