A plurality of electronic data processing machines comprised of remote personal computers, workstations, or the like, and a central monitoring host computer are interconnected to a conventional alternating current power bus. Each machine includes a power line modem for modulating and demodulating digitized data and control signals on to an off the power bus, respectively. The remote machines further include system software which digitizes a prompted-for user I.D. and respective unique machine I.D. code, stored in BIOS or other ROM, in the machine's operating system, or in DASDI in hidden files, and transmits, via modulation onto the power bus, these digitized codes to the host computer. The host computer includes software providing the functions of monitoring all power circuits for such encoded incoming machine and user I.D. information, for updating its database of machines with this incoming data, and further providing functions allowing the central monitoring computer operator to query the database and issue polling commands to selected remote equipment. Each remote machine's software further includes routines to monitor the power bus for such incoming polls from the host and transmitting the machine and user I.D.'s previously stored to the central monitor in response to such polling requests.