A data receiving or transmitting device, having data receiving or transmitting capability, is coupled respectively from or to an AC power line through a standard light bulb socket. In one aspect, a data interface includes a data receiving device that may be configured for extracting data encoded for transmission or encoding data to be embedded and transmitted along the AC power line branch circuit. In another aspect a data receiving device includes a loudspeaker, an amplifier, and a data decoder coupled to the AC power line for playback of audio program material communicated to the device along the power line. The device screws into a light bulb socket for a "no-tools" installation.