Echo suppressors for telephone connections having long propagation times

The paper describes the principles on which the new types of echo suppressor have been designed. The performance achieved, particularly as regards mutilation, is limited by the present condition of telephone networks; if return losses could be increased, the designcould be suitably modified to take advantage of these. The methods used for theoretical analysis of the behaviour of echo suppressors in telephone connections could be applied to the study of other voice-operated devices used in telephony. Much of the basic statistical information on speech waveforms is also of wider application