Thoughts on the design of a duplex modem with echo extinction

Measures to equalize the data signals to receivers as well as suppress talker echoes in duplex data transmission are discussed. Data signals are equalized either by fixed or by adaptive equalizers. Adaptive echo cancellers can be used to cancel talker echoes. Possible arrangements for echo-cancellers and equalizers are addressed, and a suitable receiver structure for a voiceband duplex modem is derived with special regard to a largely digital design. Echo extinguishers with and without supplementary interpolation filters are compared.