Data Sheet

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66. Electronic ‘OR’ Gate
Build the circuit shown on the left. The lamp (76) will light if either the
switch (62) or the press switch (61) is pressed. This circuit represents
an OR gate. If ON = True and OFF = False, then an OR gate is best
dened as: The output is TRUE when any input is True and the output is
False only when all the inputs are False.
In this circuit, the output represented by the lamp (76) is ON (True) if
either input represented by the press switch (61) or the switch (62) or
both is ON (TRUE). The lamp (76) is OFF (False) only when both switches
are OFF (False).
67. Direct Current and Alternating Current
Build the circuit, turn on the switch (62), and press the press switch
(61) and you will see both LEDs are turned on. The batteries in your
battery module (91) are providing Direct Current (DC) to the circuit. DC
provides a constant ow of current in one direction in the circuit.
LEDs are generally driven by DC current, but the outlets in your house
provide Alternating Current (AC). Alternating current changes the
direction of the current like a sine wave. This is why you will usually see
an AC to DC adaptor between your LED TV and the plug at the end of
the cord for your LED TV. This adaptor coverts the AC current from your
house outlets to DC current needed by the LEDs in your TV set.