For the first 100 years of the telephone business, all telephone circuits were analog. They were designed around the characteristics and problems of analog current and were maximized for that use.

I was at Burr-Brown in 1988 and I knew Mark Stitt well. He was a mentor to me and I was devastated at his untimely death. He had written an amazing Burr-Brown Current Source app note 1 that I have ...