I have an existing bell system, which I can take 4 or 8 or 12V. On the door is a door bell button, the bell itself is powered by a transformer. I have connected the FreeTEC bell at the cable, then the FreeTEC bell was in continuous operation - not just when the doorbell button is pressed. I could not fix it, no matter if I went with 4 or 8 or 12V. I then finished the FreeTEC bell of the existing bell system, and run this now on the radio button - worked perfectly.