Northern Telecom Limited

Bruce L Townsend

John G Ellis

Leo L Strawczynski

Balwantrai Mistry

Raymond B Wallace

Paul N Ramsden

Stephen R Saunders

Mary L Keegstra

A voice bus on a computer backplane provides point-to-point connection between a plurality of slots on the backplane to a particular slot. Connection from the plurality of slots is provided by third connectors which lie between first and second connectors defining the slots. Connection to the particular slot is via its respective second connector. In particular, the computer backplane is physically and electrically compatible with the IEEE standard 1014-1987 defining the VMEbus. The presence of the third connector is compatible with the VMEbus standard both electrically and physically.

Voice bus for a computer backplane

In a hands free communications terminal apparatus, a loudspeaker and a microphone are permitted to be simultaneously active. A controller monitors signals in transmit and receive paths to direct operations of transversal filters to provide two echo canceller functions, one for the microphone and one for a telephone line so that most unwanted echo and feedback is removed, to prevent the howling and squealing sounds that commonly occur when the loudspeaker and the microphone are both active. Remaining echoes are removed by voice switching of loss between transmit and receive paths, wherein the amount of loss is determined in response to characteristics of the telephone line and the operating environment of the terminal apparatus.

Hands free telecommunication apparatus and method

Speech signal components in a high band of frequencies between 4 and 8 kHz are transmitted via a digital transmission channel, which carries speech signal samples at frequencies below 4 kHz and sampled at a rate of 8 kHz, by replacing the least significant bit of the samples with bits of information derived from the high band by linear predictive coding. These information bits are transmitted in frames, each frame comprising a synchronizing bit and bits representing the power of and a set of filter coefficients for the high band signal components occurring in a period corresponding to the frame duration. Each such bit is transmitted redundantly three or six times in view of bit stealing techniques already used for signalling on digital transmission links. The resulting wideband speech signal transmission is compatible with existing limited bandwidth voice channel transmission arrangements.

Transmission of wideband speech signals

A conference circuit has a plurality of ports for a corresponding plurality of conferees. Associated with the ports is a control circuit which determines whether a conferee is active, i.e. talking, or dormant, i.e. listening. The circuit applies gain to the 'active' signals and attenuates the 'dormant' signals. When a listener starts to talk, the circuit switches his port to the 'active' mode. Difficulties arise in determining when a listener becomes active, due to noise and echo with the speech signal. They are mitigated by comparing the signal from the port with an echo signal estimate derived from the echo return loss for the transmission path associated with the port. The arrangement takes account of differing echo levels for different transmission paths.

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Kanata, Canada

Bruce L Townsend