Here's some information about the 4 Digit Red Display Indicators Tachometer:

LED 4-Digit Red Display Indicators: This is a common component used for displaying numerical information. A 4-digit red LED display can show numbers from 0 to 9 on each digit. It's often used in various applications where you need to display numerical data, such as clocks, timers, counters, or measuring instruments.

Tachometer: A tachometer is a device that measures the rotational speed of a shaft or wheel, typically in RPM (revolutions per minute). It's commonly used in automotive applications to measure engine speed, but it can also be used in various industrial and scientific applications.

Hall Proximity Switch Sensor: A Hall proximity switch sensor is a sensor that uses the Hall effect to detect the presence or absence of a magnetic field. It can be used to detect the position of a magnet or a magnetic object. Hall sensors are available in different types, including NPN and PNP outputs, which determine the sensor's behavior when detecting a magnetic field.

When combining these components, you might be building a tachometer system that uses a Hall proximity switch sensor to detect the rotational speed of a shaft or wheel and then displays that speed on the 4-digit red LED display.