04017797 is referenced by 15 patents and cites 5 patents.

The present invention provides a two-way sound transducer system, including amplification circuitry within an ear-muff type attenuator, to enable the user to listen to principally voice communications (although other forms of sound can be transmitted) from a remote location and in response thereto answer a communication by talking in a natural voice, irrespective of the total surrounding noise present at the location of the user.

Title
Headset for receiving and transmitting signals
Application Number
5/547184
Publication Number
4017797
Application Date
February 5, 1975
Publication Date
April 12, 1977
Inventor
John D Laessig
Newtown Square
PA, US
Agent
William E Cleaver
Assignee
Columbia Research Laboratories
PA, US
IPC
H04M 1/05
H04B 1/44
View Original Source