SEVERAL proposed high-definition television systems are currently being tested at the Advanced Television Test Center, an industry-sponsored facility in Alexandria, Va. Next year, the Federal Communications Commission plans to select a system created by one of the following consortia - or perhaps a hybrid system - as the broadcast standard:
* NHK (Japan Broadcasting Corporation) - a system that uses analog technology.
* General Instrument Corporation, Massachusetts Institute of Technology - using digital technology.
* Zenith Electronics Corporation, American Telephone & Telegraph Company - using digital technology.
* Philips Electronics, Thomson Consumer Electronics, NBC, David Sarnoff Research Center - using digital technology.
* General Instrument Corporation, MIT - a second digital system.