Give up? Stumped? The correct answer is CHI. CHI is a coupler also known as an interface device. There are approximately six different variations of couplers. They all have one thing in common. All six were outlawed by the FCC years ago. Telephone companies, however, continue to bill their clients month after month, year after year for them. Our firm recently recovered, upon behalf of one of our clients, $9,011.66, for a coupler refund going back almost 12 years. This recovery took less than five minutes to locate!