United Networks Inc.

Manu-tronics, Inc.

Levi L Rose

Alfred M Hestad

Michael Tentler

A speaker telephone system having hands-free telephone sets with microphones and loud-speakers and including circuitry for preventing feedback between the loud-speakers and the microphones in both the transmitting and receiving modes by automatically controlling the amplification of the signals coming from the microphones and going to the loud-speakers, as a function of the signal direction, while still maintaining the microphones and loud-speakers electrically coupled to the telephone lines.

Speaker phones

A solid state subscriber station network which provides transmitting, receiving and regulating functions using a single active element. The transmitted signals, the received signals and the regulatory functions can be separately varied within proscribed limits without adversely affecting the other functions.

Growing community of inventors

Chicago, IL, United States of America

Levi L Rose