Astech, Inc.

James R Lindquist

William M Brown

In a power line carrier telephone extension system for transmitting electrical signals between the telephone line and an extension telephone over the AC electric power line available at a telephone subscriber's premises, that includes a main station for processing signals between the subscriber's telephone line and power lines and two or more extension telephones of the system that plug into the power line, means that provides for two or more of the system telephones to communicate without going on the telephone line (Intercom), even while another system telephone is engaged in an outside telephone call and means are further provided for all telephones of the system to conference in Intercom.

Power line carrier multi telephone extension system for full duplex

In a power line carrier telephone extension system for transmitting electrical signals between the telephone line and one or more extension telephones over the AC electric power line available at a telephone subscriber's premises, that includes a main station for processing signals between the subscriber's telephone line and power lines and one or more extension telephones of the system that plugs into the power line, all of which can place calls to the telephone line, answer calls from the telephone line and conference together in full duplex communication, means at the extension telephones for initiating a telephone line hold signal that is transmitted over the power line to the main station where the hold signal is detected and initiates connecting a hold impedance across the telephone line.

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Rowley, MA, United States of America

James R Lindquist