The Wall Clock System is a fully functional wall clock with a video transmitter, a miniature video camera & an antenna all concealed within the unit. To power up the camera and transmitter, simply plug the wall clock into an electrical outlet. One AA battery is still required to power the actual clock. Plugging in the power cord makes the camera and transmitter operable and begins transmission immediately to the receiver unit. On the back of the wall clock there is a channel selector switch which is used to set the channel for transmission. In situations where using more than 1 transmitter, additional units must be assigned to unique channels (2, 3 or 4).