300-In-1 Electronic Project Lab
(280-0270)                 Reading Schematics         Faxback Doc. # 19470

At first, schematic diagrams might look difficult -- but they are actually
quite simple once you get some practice with them.  Don't get discouraged
if you get confused at first.  That's normal.  Before long, you can build
a circuit just by looking at its schematic diagram.

Schematics let you quickly see what happens during connection and how the
electrons flow in the circuit.  A schematic diagram is a road map for
electronic circuits.  Electronics technicians and engineers can build
entire circuits with nothing more than a schematic diagram to guide them.
While using this kit, you can learn how to build circuits from just the
schematic.

Notice on the following schematic that some lines cross each other and
there is a dot at the point where they cross.  This means that the two
wires represented by the lines are connected together at the point
indicated by the dot.  If two lines cross without a dot, that's your clue
that the wires aren't connected.

Lines Are Connected +/+ Lines Not Connected

Often a schematic diagram does not indicate the power supply (+ and -) for
ICs so the diagram is easier to read.  This is how the kit's schematics
are made.  Yet, the ICs must always connect to power.  to show you how to
connect to power, we provided the power connections in a separate diagram.
The other parts are already mounted on the board.  See the spring terminal
number shown next to the part.  Don't confuse this number with the IC pin
numbers.

Use the following chart to read the schematic.

Name     Physical                 Description

R        Resistor                 Oppose flow of electrons
Q        PNP Transistor           Change the current flow from its
                                  collector
         NPN Transistor           to emitter depending on how much voltage
                                  is added to the base and vice versa
                                  (PNP)
C        Ceramic Capacitor         Store electric energy
         Electrolytic Capacitor
D        Rectifier Diode           Let electrons flow through them only in
         Germanium Diode           one direction
         Silicon Diode
ZD       Zener Diode               Pass electrons only when the voltage is
                                   over a certain level
U        IC 4011 (NAND Gate)       Output low voltage when all inputs are
                                   high.
U        IC 4001 (NOR Gate)        Output low voltage when either or both
                                   inputs are high
U        IC 4029 (Counter)         Count the number of pulses applied to
                                   the input and output the number of
                                   counts.
U        IC 4511                   Decodes the BCD input and displays it
         (BCD to 7-Segment         on the LED display.
         Decoder)
U        IC 4027 (Flip Flop)       Changes output when a pulse input
                                   occurs.
U        IC BA546                  Amplifies the audio frequency signal
         (Audio Amplifier)
U        IC BA10324                Compares two input signals and outputs
         (Operational Amplifier)   the result
VR       Semi-Fixed Resistor       Adjustable resistor
         LED                       Emits light when electrons flow through
                                   them
LD       LED Digital Display Display numbers or some letters
CdS      CdS Cell                  Change resistance value with amount of
                                   light that falls on them
SP       Speaker                   Converts electrical energy to sound you
                                   can hear
EP       Earphone                  Lets you listen to sounds through it
         Antenna Coil              Pick up the radio signals
         Output Transformer        Match the output of the circuit to the
                                   speaker
VC       Tuning Control            Let you tune to a specific frequency
VR       Control                   Let you change resistance values
SW       Switch                    Connects or disconnects electrical
                                   circuits
S1       Key                       Lets electrons flow when you press it
T1, T2   Terminal                  Connect external devices


(br/all-02/22/96)