EE-1

The EE-1 Buzzerphone made secret telegraphic communication possible, while non-secret telephone conversation could be carried on simultaneously over the same circuit. It can be compared with the British Fullerphone, but the Buzzerphone was much improved in compactness, weight and scheme of operation.

EE-1-A

Reference

WI PA-01 Wire Communication (Electrical-Engineering) Pamphlet no.1, May 21.1918

• Technical Regulations: The Buzzerphone Type EE-1-A, 1929