Automatic echo cancellation for an integrated services digital network interface

An apparatus for selectively canceling echo between a local communication network and an integrated services digital network, comprising:

• a send input for receiving a first multi-channel signal from a local communication network;
• a receive input for receiving a second multi-channel signal from an integrated services digital network;
• a receive output, connected with said receive input, for transmitting said second multi-channel signal to the local communication network;
• an echo canceler, connected with said receive input and with said send input, for removing echo from a channel of the first multi-channel signal, and thereby producing a third multi-channel signal having echo canceled from said channel;
• a send output for transmitting said third multi-channel signal to the integrated services digital network;
• and
• selection means for (i) monitoring a first channel of at least one of said first and second multi-channel signals, (ii) detecting a call control message within said first channel identifying the type of signal within a second channel of said at least one of said first and second multi-channel signals, (iii) determining whether said identified type of signal requires echo cancellation, and (iv) instructing said echo canceler to select said second channel for echo cancellation.

An echo canceling system for an integrated services digital network, comprising

• a send input terminal for receiving a send input signal having a plurality of B-channels and a D-channel;
• a send output terminal for transmitting a send output signal having a plurality of B-channels;
• an activation controller connected with said send input terminal for (i) detecting a D-channel message within said send input signal, (ii) determining whether said detected D-channel message includes a call control message pertaining to a call on a send-input B-channel, and (iii) producing an activation signal indicating whether echo cancellation is required for said call on said send-input B-channel;
• an echo canceler having an input path for receiving a send-input B-channel signal from said send input terminal, and an output path for providing a send-output B-channel signal from which echo has been canceled relative to said send-input B-channel signal;
• and
• a routing network connected with said output path and said send input terminal, said routing network being configured (i) for routing a B-channel signal from said output path to said send output terminal when said activation signal indicates that echo cancellation is required on the corresponding send input B-channel and (ii) for routing a B-channel signal from said send input terminal directly to said send output terminal when said activation signal indicates that echo cancellation is not required on the corresponding send input B-channel.

An echo canceling system for use with a telecommunication link in which a multi-channel signal is transmitted, said system comprising:

• a protocol controller connected to receive a multi-channel signal containing a message frame that includes a plurality of data fields, said protocol controller being formed (i) to monitor a channel of the multi-channel signal, (ii) to detect the message frame in the monitored channel, and (iii) to provide an interrupt signal when the message frame is detected;
• a processor connected with said protocol controller for receiving the interrupt signal therefrom, and, in response to the interrupt signal, (i) receive the data fields from said protocol controller, (ii) determine whether the data fields contain a call control message pertaining to a call in a second channel of the multi-channel signal, (iii) determine whether the call control signal pertains to a call requiring echo cancellation, and (iv) provide an enable signal when the call control signal pertains to a call requiring echo cancellation;
• and
• an echo canceler operatively connected with said processor to receive said enable signal and to apply echo cancellation to the second channel of the multi-channel signal.

An echo canceling system for an integrated services digital network, comprising

• a send input terminal for receiving send input signals;
• a send output terminal for transmitting send output signals;
• an activation controller connected with said send input terminal for (i) detecting a D-channel message within said send input signals, (ii) determining whether said detected D-channel message includes a call control message pertaining to a call on at least one B-channel within said input signals, and (iii) producing an activation signal indicating whether echo cancellation is required for said call on said at least one B-channel;
• and
• an echo canceler operatively connected to receive said activation signal from said activation controller for applying echo cancellation to said at least one B-channel in response to said activation signal.

A method of canceling echo within a communication link having a plurality of communication channels, comprising the steps of:

• detecting a request message to establish a call on a channel of the communication link;
• determining, on the basis of information encoded within said request message, whether the requested call is of a type requiring echo cancellation to be applied to signals communicated during the call;
• and
• applying echo cancellation to signals communicated within said channel during said call when the information encoded in said request message indicates that echo cancellation is required.