The KX-TGA710B Call Block machine easily connects to your cordless phone to block robocalls, telemarketers, and unknown International, 00-Prefix and other unwanted callers. Block up to 16,000 numbers (14,000 pre-programmed; 2,000 additional numbers can be registered manually). When an unknown call comes in, simply the press the red block call button to instantly block and register the number.