Figure 4-69 shows a diagram for an automobile alarm circuit used to detect certain undesirable conditions. The

Question:

Figure 4-69 shows a diagram for an automobile alarm circuit used to detect certain undesirable conditions. The three switches are used to indicate the status of the door by the driver’s seat, the ignition, and the headlights, respectively. Design the logic circuit with these three switches as inputs so that the alarm will be activated whenever either of the following conditions exists:

■ The headlights are on while the ignition is off.

■ The door is open while the ignition is on.

Figure 4-69

+5 V Open Closed +5 V ON OFF = +5 V ON OFF Door Ignition Lights Logic circuit Alarm +5 V LED