Jack Scanlon, the senior AT&T executive who was involved in the early development of Unix, is as reported briefly last week, leaving AT&T to join the Cambridge Technology Group, Cambridge, Massachusetts, as chief operating officer this week. Founded in 1978, the Group advises and helps companies develop open systems technology. Scanlon leaves after 17 years at AT&T Bell Laboratories, where, apart from being involved in Unix, he worked in the Data Systems Group and participated in the development of AT&T’s digital switching systems.