Elenco Upgrade Kit SC100 to SC750 - Manual (Page 71)

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Project #293 Police Siren Amplifier
OBJECTIVE: To amplify sounds from the music integrated
circuit.
Build the circuit and turn on the slide switch (S1). You will hear a very
loud siren, since the sound from the alarm IC (U2) is amplified by the
power amplifier IC (U4). Sirens on police cars use a similar circuit,
with an IC to create the sound and a power amplifier to make it very
loud.
Project #294 Lasting Doorbell
OBJECTIVE: To build a doorbell
that stays on for a while.
OBJECTIVE: To build a
clicker that stays on for a while.
Place the 10 μF capacitor (C3) on
top of the whistle chip (WC).
Press and release the press
switch (S2). It makes a clicking
sound that repeats for a while.
Build the circuit at left, note that there
is a 4-snap wire on layer 1 that is not
connected to a 3-snap wire that runs
over it on layer 3. Turn on the slide
switch (S1), then press and release
the press switch (S2). There is a
doorbell sound that slowly fades away.
When the press switch is pressed,
the transistors are supplied with
current for oscillation. At the same
time, the 100
μF capacitor (C4) is
being charged. When the press
switch is released, the capacitor
discharges and keeps the oscillation
going for a while.
Project #295
Lasting
Clicking