In circuit (b) the LED will be ON when the logic gate attached to the output pin goes "lo", i.e. the voltage is 0 V. The LED will be OFF for a logic "hi" level, i.e. the voltage is +5 V. In this case, the logic gate is sinking current.
Note: With the notch placed on the left,  pin 1 is below it. The pin numbering then proceeds in a counter-clockwise direction around the chip.
1
B
1
0
1
This part is worth 1 mark.
Table 8-2
A
0
0
Assessment: Have your circuit assessed by a lab tutor.
0
1
Figure 8-12
Note: Unused inputs should not be left "floating". Connect them to one of the logic levels - either "hi" (5 V) or "lo" (0 V). Otherwise, the chip may not work properly.
Jumper A
Jumper B
Figure 8-11
Note: Unused outputs are left unconnected.
Note: It is a mistake to wire outputs together - this can damage the chip!
(on/off)
(on/off)
LED
Wire up the logic circuit shown below. The numbers on the wires represent the pin numbers on the package.
A suggested breadboard wiring diagram is shown below. Use different coloured wires for the connections.
Test the following jumper combinations, noting the condition of the LED.
Verify that you can wire switches to give a 2-way switching function, by constructing the circuit shown below. Use jumper wires to simulate switch contacts.
Now test your circuit to ensure that it gives the desired results. Fill in the truth table in Table 8-2 below:
𝐴
Figure 8-10
Table 8-1
𝐴
𝐵
𝐵
𝐴
𝐵
𝐴
𝐵
LED