Phone Message Monitor

摘要

For years I had a common wall-mounted telephone. It featured an LCD, stored a dozen or so phone numbers, and could redial-all of which are basic features by today's standards. Nothing to get excited about. But it had a big red light flashing when there was a waiting voice message. When the phone eventually went to telephone heaven, I scoured the Internet to find a replacement, but all telephones claiming to have a message waiting function put just a little icon on their LCDs. No more flashing red light. In addition to the easy-to-miss icon, "message waiting" is indicated by a stuttered dial tone (SDT) when you pick up the phone to initiate a call. There is no indication when you receive a call. Being used to the flashing red light we missed messages or responded to them late. So I decided to build a message waiting monitor with a flashing red light that could be installed inside a telephone.