I have a barcode printer with a verifier attatched. When the verifier senses a bad label, it throws the printer into an error condition, and an error LED blinks. I would like to use this blinking LED signal to trigger an audible alert. I have traced the line that carries the flashing voltage, which in a normal state (non-error) is 3.5VDC. When the error light is flashing, the voltage is alternating between 2.5vdc and 3.5vdc, with the light coming on at peak. I measured from line to chassis ground. This isnt what i expected to find, but why it works that way doesnt really matter if i'm correct in how i want to use it.<br> I intend to have the buzzer on its own self-powered circuit. I have a 27VDC or 5VDC auxiliary power supply to use for the buzzer. My plan is to use the 3.5VDC to bias a transistor at the Collector, and use the drop in voltage as the trigger to close the Base-Emitter switch, turning on the buzzer. Can anyone tell me if i have the configuration correct, and if not, please tell me the right arrangement. Also, what transistor and/or buzzer do you recommend for those operating ranges?<br>