# US 7,609,646 B1 · Method and apparatus for eliminating false voice detection in voice band data service > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,646 B1 - Document ID: US7609646B1 - Status: Granted - Kind: B1 - Application number: 10/825,030 - Filed: 2004-04-14 - Granted: 2009-10-27 - Earliest claimed: 2004-04-14 - Assignees: Cisco Technology, Inc. - Inventors: David Cheng-Song Qi; Yan Wang; Timothy G. Wade - Web page: https://patentgrep.com/patent/US7609646B1 ## CPC - H04L 12/66: Arrangements for connecting between networks having differing types of switching systems, e.g. gateways - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A system in a Voice Over Internet Protocol (VOIP) network eliminates false voice detection in voice band data service (e.g., modem or facsimile transmission) by sequentially enabling silence detection then voice detection. In Voice Band Data (VBD) mode, the system initially enables silence detection and disables voice detection. If silence is detected in a VOIP signal associated with a VOIP call, the system enables voice detection. If voice is detected, the system switches from VBD mode to voice mode and enables processing (e.g., echo cancellation and/or data compression) that improves voice communications. ## Claims ### Claim 1 A method operating in a device that couples circuit switched and packet switched networks for eliminating false voice detection in Voice Over Internet Protocol (VOIP) service supporting a voice band data mode and a voice mode, the method comprising: in voice band data mode, enabling silence detection and disabling voice detection from detecting a voice band signal associated with a VOIP call; monitoring the voice band signal for silence; while remaining in the voice band data mode with silence detection enabled, in response to detecting silence for a predetermined length of time, enabling voice detection; if voice detection is enabled, monitoring the voice band signal for voice; and in response to detecting voice, terminating voice band data mode and entering voice mode. ### Claim 2 (depends on 1) The method according to claim 1 wherein, if the silence detected is shorter than the predetermined length of time, continuing in voice band data mode and disabling voice detection. ### Claim 3 (depends on 1) The method according to claim 1 wherein, if voice detection is enabled, in an absence of detecting voice, continuing in voice band data mode. ### Claim 4 (depends on 1) The method according to claim 1 wherein detecting silence includes terminating the voice band data mode if silence exceeds a second predetermined length of time. ### Claim 5 (depends on 4) The method according to claim 4 wherein the second predetermined length of time is at least two seconds. ### Claim 6 (depends on 1) The method according to claim 1 wherein detecting silence includes detecting silence in a bi-directional manner. ### Claim 7 (depends on 6) The method according to claim 6 wherein enabling voice detection occurs in response to detecting silence for at least 250 msec. ### Claim 8 (depends on 1) The method according to claim 1 further including disabling echo cancellation in voice band data mode and enabling echo cancellation in voice mode. ### Claim 9 (depends on 1) The method according to claim 1 wherein the device is a gateway. ### Claim 10 (depends on 9) The method according to claim 9 wherein the gateway is a terminating gateway. ### Claim 11 (depends on 9) The method according to claim 9 wherein the gateway is an originating gateway. ### Claim 12 (depends on 1) The method according to claim 1 wherein the device is external from a gateway. ### Claim 13 (depends on 12) The method according to claim 12 wherein the device is between the terminating gateway and an answering modem. ### Claim 14 An apparatus for eliminating false detection in a Voice Over Internet Protocol (VOIP) service supporting a voice band data mode and a voice mode, the apparatus comprising: a communications bus carrying voice band signals associated with a VOIP call; a silence detector coupled to the communications bus configured to (i) detect silence on the bus and (ii) enable in voice band data mode; a voice detector coupled to the bus configured to (i) detect voice on the bus, (ii) initially disable the detection of the voice band signals in voice band data mode, (iii) while remaining in the voice band data mode with the silence detector enabled to detect silence on the bus, enable voice detection in response to the silence detector's detecting silence for a predetermined length of time, and (iv) monitor the voice band signals after being enabled; and a processor, coupled to the silence detector and the voice detector, that terminates voice band data mode and enters voice mode in response to the voice detector's detecting voice on the communications bus. ### Claim 15 (depends on 14) The apparatus according to claim 14 wherein the processor continues in voice band data mode if the silence detector detects silence for less than the predetermined length of time. ### Claim 16 (depends on 14) The apparatus according to claim 14 wherein, if the voice detector is enabled, the processor disables the voice detector and continues in voice band data mode in an absence of an indication from the voice detector that voice is detected. ### Claim 17 (depends on 14) The apparatus according to claim 14 wherein, if the silence detector detects silence for a second predetermined length of time, the processor terminates the voice band data mode. ### Claim 18 (depends on 17) The apparatus according to claim 17 wherein the second predetermined length of time is at least two seconds. ### Claim 19 (depends on 14) The apparatus according to claim 14 wherein the silence detector detects silence on the communications bus in a bi-directional manner. ### Claim 20 (depends on 19) The apparatus according to claim 19 wherein the voice detector enables in response to the silence detector's detecting silence for at least two seconds. ### Claim 21 (depends on 14) The apparatus according to claim 14 further including an echo canceller disabled in voice band data mode and enabled in voice mode. ### Claim 22 (depends on 14) The apparatus according to claim 14 deployed in a gate way. ### Claim 23 (depends on 22) The apparatus according to claim 22 deployed in a terminating gateway. ### Claim 24 (depends on 22) The apparatus according to claim 22 deployed in an originating gateway. ### Claim 25 (depends on 14) The apparatus according to claim 14 deployed external from a gateway. ### Claim 26 (depends on 25) The apparatus according to claim 25 deployed between the terminating gateway and an answering modem. ### Claim 27 A computer-readable medium having stored thereon sequences of instructions, the sequences of instructions, when executed by a digital processor, cause the processor to: for a Voice Over Internet Protocol (VOIP) call, enable silence detection and disable voice detection from detecting a voice band signal in voice band data mode; monitor a voice band signal associated with the VOIP call for silence; while remaining in the voice band data mode with silence detection enabled, in response to detecting silence for a predetermined length of time, enable voice detection; if voice detection is enabled, monitor the voice band signal for voice; and in response to detecting voice, terminate voice band data mode and enter voice mode. ### Claim 28 (depends on 27) The computer-readable medium according to claim 27 wherein the sequences of instructions cause the processor to continue in voice band data mode and disable voice detection if the silence detected is shorter than the predetermined length of time. ### Claim 29 (depends on 27) The computer-readable medium according to claim 27 further including instructions to cause the digital processor to continue in voice band data mode in an absence of detecting voice if voice detection is enabled. ### Claim 30 (depends on 27) The computer-readable medium according to claim 27 wherein the instructions that cause the processor to detect silence include instructions that cause the processor to terminate the voice band data mode if silence exceeds a second predetermined length of time. ### Claim 31 (depends on 30) The computer-readable medium according to claim 30 wherein the second predetermined length of time is at least two seconds. ### Claim 32 (depends on 27) The computer-readable medium according to claim 27 wherein the instructions that cause the processor to detect silence include instructions that cause the processor to detect silence in a bi-directional manner. ### Claim 33 (depends on 32) The computer-readable medium according to claim 32 wherein the instructions that cause the processor to detect silence include instructions that enable voice detection in response to detecting silence for at least about 250 msec. ### Claim 34 (depends on 27) The computer-readable medium according to claim 27 further including instructions that cause the processor to disable echo cancellation in voice band data mode and enable echo cancellation in voice mode. ### Claim 35 (depends on 27) The computer-readable medium according to claim 27 used in a gateway. ### Claim 36 (depends on 35) The computer-readable medium according to claim 35 wherein the gateway is a terminating gateway. ### Claim 37 (depends on 35) The computer-readable medium according to claim 35 wherein the gateway is an originating gateway. ### Claim 38 (depends on 27) The computer-readable medium according to claim 27 used in a network device external from a gateway. ### Claim 39 (depends on 38) The computer-readable medium according to claim 38 wherein the network device external from a gateway operates between a terminating gateway and an answering modem. ### Claim 40 An apparatus for eliminating false detection in a Voice Over Internet Protocol (VOIP) service supporting a voice band data mode and a voice mode, the apparatus comprising: means for enabling silence detection and disabling voice detection from detecting a voice band signal for a VOIP call in voice band data mode; means for monitoring a voice band signal associated with the VOIP call for silence; means for enabling voice detection in response to detecting silence for a predetermined length of time while remaining in the voice band data mode with silence detection enabled; means for monitoring the voice band signal for voice if voice detection is enabled; and means for terminating voice band data mode and entering voice mode in response to detecting voice.