Intercommunication systems

Washington, D.C. Miss Mabel Stargel talks into a microphone of the office intercommunication system at Western Union telegraph office

92 Adalbert Strasse, Berlin, 2014

Building systems

Public address systems

Rep. Vincent Morrison Brennan, Republican of Michigan, listening in on the proceedings of the House, with a receiving set

Postmaster General Work and his assistants inspecting the Radio equipment recently installed on aero mail planes

Communication devices

Intercoms (Not Used for Indexing)