The application of power electronics to facilitate the transmission or conversion of electric energy has been well known. This paper presents a different class of power electronic applications-the power electronic circuits are deployed to create small but discernible signals online. The signals are utilized for monitoring, power line communication and other information-oriented purposes. We use the term “power electronic (PE) signaling technology” to designate the technologies involved in these applications. The objective of this paper is to survey and review the developments in this fascinating field. Several highly successful PE signaling technologies and their applications are illustrated. It is believed that signaling-oriented power electronic techniques will have many potential applications in power systems and can be a major source of innovation for the smart grid initiative.