Many years ago, I had a land-line service that allowed my phone to ring only if the number was available via Caller ID and was on a white-list of numbers. Any

Many years ago, I had a land-line service that allowed my phone to ring only if the number was available via Caller ID and was on a white-list of numbers. Any other caller would hear a message prompting for a touch-tone code to ring our phone. ( Critical people knew this code in case they called from a phone outside of the white-list ). If the caller couldn't enter the touch-tone, they went right to voice mail. The phone wouldn't ring, but the voice-mail indicator would show if they had taken the time to leave a message.