Carl A. Dahlbom, one of the key figures behind multifrequency (MF) signaling, died last week at age 93. If you've ever heard and enjoyed those quick little tones after you dialed a long-distance call, or if you've ever used a blue box, Carl is the man you have to thank for it. He is probably most famous for the article "Signaling Systems for Control of Telephone Switching", co-authored with C. Breen for the November 1960 issue of the Bell System Technical Journal.
His obituary can be found at:
formatting link
Instead of a moment of silence, honor Carl with a burst of 2600 Hz followed by some MF tones.
Phil