this is a security system that uses ultrasonic sensor, piezo buzzer, and lcd. it also has buttons to increase and decrease the range for the ultrasonic sensor.

All students are safe after a Lincoln elementary school went into lockdown for a 26-year-old man attempting to enter the ...

It detects intruders, measures distances, monitors sound levels, and senses vibrations. Upon detection of suspicious activity, the system triggers SMS alerts using the SIM900A GSM module, providing ...