The SR-3 selective ring call router is a cost-effective device that automatically routes incoming phone calls based on learned ring cadences, allowing multiple numbers to be used on a single line without the need for additional programming. It supports various applications like voice mail, call forwarding, and is compatible with home and business setups, ensuring calls are directed correctly. With a small footprint and user-friendly installation, it promises a return on investment within three months and includes optional features like barge-in protection.