The Hopkins Mfg Corp. 374-39302 Digital Classic Alert System is a wireless security system that uses a digital radio frequency to send alerts to your security system. The system includes a receiver, transmitter, and a keypad. The receiver is placed near the entrance of your home or business, and the transmitter is placed in a secure location. When an alarm is triggered, the transmitter sends a signal to the receiver, which sends an alert to your security system. The keypad allows you to easily access the system's settings.