[Sender frames, dial equipment.]
[District selector frame in a dial exchange.]
[General view of sender frames in a panel dial central office.]
[People observing telephone operators.]
Communications, Telephone Exchange.
Telephone, New York Telephone Co. Exchanges.
[Early types of switchboards, Old Spring Exchange.]
[Early types of switchboards.]
[Overseas switchboard at 32 Avenue of the Americas.]
The Simen Automatic Signal System.