A push on the outdoor-mounted bell activates a strobe light and chime on the wireless receiver. Receiver can be placed anywhere—on a nightstand, in the kitchen, etc. Simple and easy to install. 4 sound/strobe options. Doorbell Receiver (Strobe Chime) requires 3AA batteries (not included). Transmitter (button) requires CR2032 coin cell battery batteries (included). 3.5” x 2.5” x 4.75”.