10D is a block diagram of a doorbell camera system that has a voltage monitoring unit in a bypass unit in accordance with some implementations. The doorbell camera system 1000 includes a doorbell camera 106 having a doorbell button 1002, a camera module 1004, an LED indicator, a speaker, a microphone, a processor and memory including programs executed by the processor. The camera module 1004 further includes a lens assembly 704 and an image sensor array that are configured to capture images at a premises, and a wireless transceiver that is configured to exchange data with a remote server over one or more wireless communication networks. The doorbell button 1002 is configured to trigger a remote chime 1006 in response to a user press on a button top 702. In some implementations, the LED indicator is configured to illuminate through a peripheral edge 1040 of the doorbell button 1002 that surrounds the button top 702. The doorbell camera 106 is electrically coupled to the remote chime 1006 via a bypass unit 1012 powered by a transformer 1010 that provides an input AC voltage e. g. , by converting a mains power supply of 110V to the input AC voltage of 8V, 10V or 12V. The remote chime 1006 is configured to ring in response to a press on the doorbell button 1002. In some circumstances, a conventional doorbell is electrically coupled to the remote chime 1006 that is further coupled to the transformer 1010. When the doorbell camera 106 replaces the conventional doorbell, the remote chime 1006 is disconnected from the transformer 1010 and the doorbell, and replaced by the bypass unit 1010.