AT&T; Expected to Take Big Writedown

American Telephone and Telephone Co. is expected to announce today that it will write off or more quickly depreciate billions of dollars of aging network facilities, industry analysts said Wednesday.

They said the accounting changes, prompted by AT&T;’s decision to speed up the modernization of its network, could cover up to $5 billion worth of equipment and will likely erase most of its earnings for the year.

AT&T; said in October that such steps were likely in the fourth quarter but put off a final decision until later in the year.

The company said it will hold a news conference today at its New York headquarters but refused to disclose the topic of the briefing.

In the first nine months of the year, AT&T; earned $587 million, or 55 cents a share.

Analysts expect a combination of a writedown, leading to a charge against earnings that may exceed $3 billion, and faster depreciation, which would reduce earnings by increasing depreciation reserves.

The initial result would be a huge fourth-quarter loss--perhaps as much as $2 a share. But analysts said AT&T; must write off its old network and speed deployment of digital switching and transmission gear if it is to stay competitive with MCI Communications Corp. and US Sprint Communications Co., which have already digitized much of their networks.

The analysts said the move should boost earnings in 1989 by lowering AT&T;’s operating costs and depreciation expenses.