Case study: Phone chip: Shared circuits save space

For nearly 10 years, engineers at AT&T´s Consumer Products Laboratory wanted to put the basic circuitry of a telephone onto a single chip, but manufacturingcost estimates held them back. In 1984 they started work on a chip that incorporates ringer, dialing, and power-conditioning circuitry on a single bipolar die. The chip was first used in AT&T´s Model 1600 Featurephone, introduced in August 1985.