I used a Bosch type 5 pin relay. This diagram show what mine looks like with oil pressure. Term. 86 is not grounded, term. 30 to 87a is normally closed. When oil pressure is 0, 86 grounds and 30 to 87 closes and 87a opens. In my case, I lose power to my fuel pump. In your case, your buzzer would be wired to 87 and you gain power to the buzzer.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.