This article from Popular Electronics dated 1956 reads: "Telephone users will welcome the news that the Bell Telephone Laboratories is experimenting with a new device that will eliminate the b-r-r-r-ing of present-day instruments. The gadget, using transistors, will produce pleasant musical tones resembling those of a clarinet. Sound emanates through the louvred area at the base of the set, shown in the photo with a white background."
Read the Modern Mechanix blog for more of these jewels. Love their tagline: "Yesterday's tomorrow, today." And as a Friday bonus, see this 1958 Popular Science feature on subliminal advertising and preconscious television.