dougc@uswest.com (Doug Corey) (12/15/89)
There was a question a short time back about how to replace stutter dial tone with a message waiting light. This is available at least to certain US customers with Centrex, Centron, or single line service provided that service is off an appropriate switch (1AESS, 5ESS and, I believe NT switches, running the appropriate generic) and provided the voice mail system sends the right signals to the switch (if you get stutter dial-tone, it probably does). AT&T (I think) came up with this service a couple of years ago. In general its called "Message Service System" and includes "The Bulk Calling Line Message Service", "Individual Calling Line Message Service", "The Visual Message Waiting Indication Service", and "Message Waiting Indication via the I/O Channel for Bulk Calling Line Message Service". The specifications and message formats are described in an AT&T Technical Description, CIR 231-099-022TD (the copy I'm looking at is labeled "Issue 3", and dated February, 1987). As far as "turning on the light" goes, the voice mail provider sends a request to the switch which tells it to provide stutter dial-tone, and/or send a message over the customer's line (using FSK signalling) to alert a "light box" which is bridged on the line at the customer's premise. Messages are only sent while the phone is on-hook or during the silent interval of ringing (latter case I suppose for calling number ID). AT&T (and perhaps others) sells a "light box receiver" and a telephone equipped with the equivalent circuitry. I seem to have tossed the flyer I had so I don't recall the model numbers but as I recall the light box lists for around $50, the phone with the light for a few dollars more. I've never tried to buy one. I suppose you could start with your friendly neighborhood AT&T phone center.