Spinout, hit the nail on the head!!!!
Yes! I completely forgot that we had that intercom system!!! Actually, in our house it was a necessity. My mother worked at home on the third floor of a four floor walk-up in NYC. She received and sent packages all day long via a messenger service and they had to get through two security doors with electrically-controlled locks. When the doorbell rang she'd use the intercom to see who was there and then use a feature built-in to it to unlock the doors. As kids, of course, we also used it to spy on the other family living in the building but got in severe trouble if we were caught.