Abstract: Disclosed is a power line transmission system which generates a narrow band multi-frequency shift keyed signal having a first predetermined frequency representing a first state of information (e.g., a "0") and a second predetermined frequency representing a second state of information (e.g., a "1"). The system includes a power line connected between a transmitter and a receiver and the FSK narrow band signal is transmitted from the transmitter over the power line to the receiver which recovers the transmitted information. The system provides improvement over noise problems present in a power line and in addition provides multi-channel capability.

Abstract: A message communication system which provides instant messages and memoranda at a telephone user's desk. In an office complex, a message is transmitted over pre-existing office power lines to printers located in a user's office and is automatically posted with time of day, date and sequence number. When a telephone call cannot be completed, messages are entered at the terminal by a telephone operator or message attendant. A computer automatically formats message forms and stores the text on a magnetic diskette. Messages are transmitted to outlying printers and can be recalled for display or resending at any time.