An alarm with delayed trigger can be made using electronic scheme below. This electronic alarm becomes operational after about 30 after the input becomes 0 emitting four sounds at one second interval. This operation is repeated every thirty seconds until the input signal reaches a logic state 1 again.
The circuit is realized with binary counters with 14 stages, with oscillator built realized in CMOS technology type 4060. Oscillator frequency, f is determined by following formula f = 1/4R3C1, where f is in Hz, in ohms R3 and C1 in farads.