Though they used separate incoming and outgoing frequencies, these frequencies were beyond the voiceband for which the cables were designed, and often suffered attenuation distortion due to incomplete impedance matching, including narrow frequency gaps that could not be made usable by echo cancellation.
Though they used separate incoming and outgoing frequencies, these frequencies were beyond the voiceband for which the cables were designed, and often suffered attenuation distortion due to bridge taps and incomplete impedance matching. Deep, narrow frequency gaps often resulted, that could not be made usable by echo cancellation.