The Fairfax County Board of Supervisors voted yesterday to give county residents a break on escalating local phone costs by exempting part of monthly telephone bills from a utility tax.

The action removing the county's 22.2 percent telephone utility tax from the first $5 of each residential bill will mean a saving of about a dollar a month for most residents.

In other actions, the supervisors approved a county-run feeder bus system in the area around the Huntington Metro station and endorsed the idea of placing a ceiling on the amount county employes can be paid in combined county retirement benefits and salary.

The supervisors unanimously approved the tax cut after citing complaints over several months that phone bills have increased dramatically since the AT&T divestiture.

The change in the tax structure, which will become effective March 1, will not cover long distance service bills, officials said.

The telephone tax reduction was the first of several fee and tax cuts suggested by board members.

Several members have said they will propose reductions in property tax rates because large county budget surpluses have become the norm. Last week the board asked the county Water Authority to consider cutting its water service rates because of a large budget surplus in that agency.

County officials said the experimental county-run feeder bus system the board approved yesterday to replace Metrobus service in the area of the Huntington Metro station can save taxpayers about $300,000 next year. It will begin operating in April if also approved by the Metro board as expected.

The county has approved restructuring about 21 current Metrobus routes, tying most of them to rush-hour service.

County officials, who have long criticized the high expenses of operating Metrobus service, say the experiment could lead to the county taking over more of the suburban bus service.

Metro would operate the feeder bus system during a transition period, with the county taking total control of it next September.

Board members tangled, as they have before, over a proposal to ban so-called "double-dipping" by county employes who retire from one department of the county government and return to a different department, drawing both their pensions and new salaries.

Annandale Supervisor Audrey Moore, a Democrat, asked the board to eliminate "double-dipping" and labeled the county's policy, one of the most liberal in the Washington area, "a ripoff."

County officials have identified at least 25 employes who draw county pensions in addition to their salaries at an estimated cost of more than $898,000 this year.

But the proposal to eliminate the practice drew loud protests from fire and police officials, who said their employes traditionally retire earlier than most other county employes and frequently move into other forms of government service.

Instead of adopting Moore's proposal, the board decided to endorse the concept of placing a ceiling on the amount of money an employe can receive from combined county retirement benefits and salary. The county staff was instructed to draw up details of such a ceiling.

"We're hiring a number of retired employes from other jurisdictions," said Mason Supervisor Thomas M. Davis, a Republican. "Under this plan we hire our own employes and make money on the deal."

Moore disagreed, casting the lone dissenting vote: "We've talking about anywhere up to $75,000 as a cap," she said. "That's too much."