General Description The SVD 588 consists of an internal pickup AC sensor plate, a test(oscillator) and diagnostic circuit, an adjustable threshold comparator, a sound annnunicator(buzzer), a visual indicator(super high bright LED) and a 9V battery. all enclosed into the robut " beeper" style case. Principle of how it work The SVD-588 detects AC voltage using its internal AC sensor plate. The AC sensor plate pick up part of the radiated electric field in volts per meter (V/M). The electric field is amplified and processed by the internal circuitry and once the processed signal is above the threshold, triggers the input of a integrated circuit, which start the oscillator for the buzzer and LED. The buzzer beeps and LED lit intermittently at a rate of 2 beeps/flash per second. The "Self-test" diagnostic is actioned by depressing simultaneously both push button on the front panel. The battery monitoring is always ON.