Salt Lake County commissioners have given businesses and outdoor advertising companies five years to bring all signs in unincorporated areas into compliance with the county's sign ordinance.

Commissioners amended the ordinance last week, adding a controversial so-called amortization clause that sets a Jan. 1, 1994, compliance deadline.An updated sign ordinance establishing tougher size, height and setback regulations for signs was approved by commissioners earlier this year. The regulations vary according to zoning classification.

The intent is to protect residential neighborhoods from signs that, because of extreme size or height or poor location, are offensive.

But when the ordinance was passed in April, commissioners agreed to negotiate the amortization clause - which sets a deadline for compliance with the ordinance - with outdoor advertising companies and businesses.

Advertisers have argued that setting a compliance deadline would force them to tear down existing signs that don't comply with the ordinance, causing loss of revenue and added expense possibly totaling millions of dollars.

Because signs have a limited product life and must eventually be replaced, the businesses had asked that nonconforming signs be allowed, under a grandfather clause, to remain in place until they reached the end of use. Then they could be replaced with signs that conform to the law.

But the negotiations on the amortization clause weren't fruitful, so the commission decided on five years as a reasonable amortization period - one that commissioners feel is likely to withstand a legal challenge, should sign companies take their fight to court.