1 An alarm circuit is needed to indicate that either the tem

1. An alarm circuit is needed to indicate that either the temperature or the pressure in a batch process is too high. If either of the conditions is true, a microswitch closes to ground, as shown in figure 1. The required output for an LED is a LOW signal when the alarm condition is true. George thinks that an OR gate is needed, but Betty argues that an AND gate is needed. Who is right and why?

Figure 1 is shown in here: http://imgur.com/3V9A0CF

2. A car burglar alarm has a normally LOW switch on each of its four doors when they are closed. If any door is opened, the alarm is set off. The alarm requires an active-HIGH output. What type of basic gate is needed to provide this logic?

3. Assume you were troubleshooting a circuit containing a 4-input NAND gate and you discover that the output of the NAND gate is always HIGH. Is this an indication of a bad gate? Explain your answer.

Solution

1)

Truth table:

The correct choice of gate is OR and inverter (or) NOR gate, where Nor Gate only give the output is 1 when both input are0,for other choice of input its gives 0. its the need for this logic.

2)According to this condition when any one of the input is active High then The output is active high, for this we need 4 input OR gate.

3)yes its bad gate, since when all the four input of NAND gate is high it must ouput to be 0, but its giving output as 1.