Importance

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Abstract

Each of a plurality of message terminal units (10, 12, 14, 16) has a keyboard (20) for entry of data, a visual display (22) for display of entered and received data, and a logic system (FIG. 4) for processing received and transmitted messages. Each unit stores in a CPU (52) a dedicated user terminal identification. Each transmitted message is annexed to a destination terminal identification and said user terminal identification (FIG. 5). Only a unit with a stored user identification identical to the destination identification in a transmitted message can receive and display transmitted messages. Upon receipt of a message, a terminal sends an automatic response to the sending terminal, which provides an appropriate indication to the sender. The receiver can send a manual acknowledgement (42) to the sender, which causes the message to be cleared from the sender's display. The units transmit messages via pulse modulation of a high frequency carrier over a supply power line (26) so that no special wiring is required. A unit can send messages to plural destinations and indicate which destination units have received the message. Optionally, a user can store plural incoming messages (FIG. 7) and selectively display same. Also, optionally, a unit can send its user's identification indicia, upon attempted entry thereof, to all other units which will compare the attempted identification entry indicia with their stored user identification indicia (FIG. 8) and indicate if the same indicia are already in use, thereby preventing two users from using the same indicia so as to insure privacy of transmission. A unit can be made to automatically send a fixed message upon receipt of any message, this feature being most useful to indicate a user's temporary absence.

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First Claim