Echo Suppressors for Long Telephone Circuits; Bell Telephone Laboratories Reprint B-165-I, november 1925. A. B. Clark, R C. Mathes.

Echo Suppressors for Long Telephone Circuits; Bell Telephone Laboratories Reprint B-165-I, november 1925.

Bell Telephone Systems NY 1925, 24 pages, photographs.

Condition: Very Good, light blue heavy paper covers, stapled wraps, three-hole punched at margin, sound and secure, pages clean and unmarked.

Price: $5.00

Item Description

A Discussion of the elimination of echoes in long four-wire and two-wire telephone circuits by means of switches controlled by rectified voice currents.