Data Sheet

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74. Triple Input ‘OR’ Gate
Build the circuit shown on the left, making sure all switches are OFF.
The lamp (76) should be OFF. Turn ON any one of the switches and the
lamp (76) will be ON. To turn OFF the lamp (76), all of the switches
must be OFF.
Electronic OR Gates can have two or more inputs but the function is still
the same. All inputs must be False (OFF) for output to be False (OFF).
75. Series-Parallel Circuit Paths (I)
Build the circuit shown on the left. In this circuit, the lamp (76) that
indicates current ow cannot turn ON by just turning the switch (62)
ON. If you turn the switch (62) ON and press and hold the press switch
(61), then current will ow. Or if you turn the switch (62) ON and move
the magnet (7) towards the reed switch (83), then current will ow.
Since the switch (62) is in series with the other two switches that are in
parallel, this makes a series-parallel circuit path for the lamp (76). This
kind of circuit could be used in a hotel room where your key card must
be inserted in a card holder near the door to enable a closed circuit,
but you still need to turn on switches in the room to have certain lights
or devices close the circuit and turn on.