The BT Ambassador is a telephone private branch exchange switchboard.
Manufactured for BT by the General Electric Company, it was discontinued in 1991.
Both systems used proprietary phones, allowed direct access to outside lines (with lamp indication), had an intercom facility and allowed basic call diversion.
Used Ambassador and Senator equipment is available on the second hand market in the United Kingdom.
These days they could provide intercoms facilities for private homes but do not have much use in a modern office, due to lack of features and interoperability.