Police and Fire Department emergency switchboards were swamped with more than 500 calls yesterday after the first joint sounding of city and county air raid sirens.

City Civil Defense Director Richard F. Lynch attributed the extraordinary number of calls to county participation for the first time.  Far Eastern "tension" and the recent report on "devastating effects of the hydrogen bomb and its lethal fallout pattern"

A month ago, he pointed out, only 25 calls were received in the routine 10 a.m. statewide "white alert" test, which is the "all clear" signal.

Most of yesterday's calls, he said, involved request for "protection" information, such as details on home bomb shelter construction and types of foods to be stored away for an emergency.

Joining in the test were 24 new county sirens in unincorporated county areas, installed at a cost of $200,000. 

County Civil Defense Director Howard Earl said reports from the outlying areas indicated the tests were clearly audible and "very satisfactory."