There is disclosed a data receiving device for coupling to an AC power line through a standard light bulb socket. A standard medium lamp base is supported by a frame and connected to a branch circuit of the AC power line. An electrical device having signal terminals and supported by the frame is driven by electrical circuitry having a first input and a first output. The first output is coupled to the signal terminals for driving the electrical device. A data receiver has a second input for receiving both AC power and a data signal from the AC power line. The second input is coupled to the lamp base and a second output is coupled to the first input of the electrical circuitry.In another aspect, a data interface comprising a standard medium lamp base coupled to a data terminal device having a data receiving and/or transmitting interface circuit therein is threadably engaged to a standard medium lamp receptacle connected to the AC power line branch circuit. The data receiving and/or transmitting interface circuit, or data modem, in the data terminal device is configured for extracting data encoded for transmission or encoding data to be embedded and transmitted along the AC power line branch circuit.