Hacking the House: Chapter 1 - The Chicago doorbell

In this paper, the author discussed how he hacked the lobby-level door of their multitenant rental apartment building so that newspapers can be delivered at their apartment unit. An out-of-phase 24-V AC transformer gave him a virtual access to the bottom of the door strike coil. By adding a time-of-day switch along with a current-limited 24-V DC power supply in his apartment, he was able to unlock the front door during the early morning hours when the newspaper carrier needed access to drop off his newspaper. By using 24-V DC, there was no buzz on the door strike.