Mary Kay Johnson, director, advertising sales, MediaOne, Los Angeles, joins AT & T Broadband, Los Angeles, as GM, media services.

Gary MacGregor, director, corporate marketing, Triax Telecommunications Co., Bel Air, Md., joins Comcast Cable, Dover, Del., as marketing director.

Mark S. Williams, director, engineering and operations, Cox Communications Inc., Atlanta, named VP, operations engineering.

Appointments at Insight Communications, Boston: Susan Chavarria, sales manager, Slingshot Networks, Washington, named Mid-Atlantic regional sales manager, there; Marianne Hartman, manager of event operations, United Artists'Satellite Theater Network, Denver, named Central regional sales manager, there.