# Identifying the logic gate needed for this problem

Problem:

4  Q20.   Sensors are used to monitor the pressure, volume, and temperature of a chemical solution stored in a vat.

The circuitry for each sensor produces a HIGH voltage when a specified maximum value is exceeded. An alarm requiring a LOW voltage input must be activated when either the pressure, temperature or volume is too high.

The vat sensor consists of a single logic gate whose inputs are connected to the pressure, temperature and volume sensors (one sensor per input), and whose output is connected to the alarm.

What type of logic gate is needed to implement the vat monitor?

The solution to this problem states that the required gate is a NAND gate. I found it to be a NOR gate.

My reasoning was that since any 1 (input) was cause for the alarm to activate (needed a LOW), a NOR gate was required. Clarification is needed.

## 1 Answer

It's definitely a 3-input NOR gate.

P V T A
0 0 0 1
1 X X 0
X 1 X 0
X X 1 0

• I knew it... the solution is wrong. It stated "It must be a NAND gate.". Ridiculous. – The Audience Mar 17 '15 at 17:21