Three-way call detection system

• US 5,768,355 A
• Filed: 05/16/1996
• Issued: 06/16/1998
• Est. Priority Date: 05/16/1996
• Status: Expired due to Term

• Current Assignee: Lattice Incorporated
• Original Assignee: Lattice Incorporated
• Inventors: Shenoi, Kishan, Spadaro, Thomas R., Jaeger, Michael S., Salibrici, William
• Primary Examiner(s): Zele, Krista
• Assistant Examiner(s): Wolinsky, Scott
• Application Number:
  US08/649,071
• Time in Patent Office: 761 Days
• Field of Search: 379/24, 379/34, 379/35, 379/93.01, 379/188, 379/189, 379/199, 379/201, 379/202, 379/215, 379/377, 379/386, 379/393, 379/410, 379/421, 379/424, 379/251, 379/204, 379/205 , 379/206, 370/260, 370/261, 370/262, 370/263, 370/270
• US Class Current: 379/189
• CPC Class Codes: H04M 3/002 Applications of echo suppressors or cancellers in telephonic connections in two-way loud-speaking telephone systems H04M9/08, echo suppressors or cancellers per se H04B3/20
• CPC Class Codes: H04M 3/56 Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities video conference systems H04N7/15
• CPC Class Codes: H04M 3/568 audio processing specific to telephonic conferencing, e.g. spatial distribution, mixing of participants echo suppression in two-way loud-speaking telephone systems H04M9/02; sound field processing per se H04S7/30

Abstract

Disclosed is a three-way call detection system that uses digital signal processing to identify a third party connection. The disclosed invention operates by establishing a baseline ambient, or background, noise level, and detecting when the signal noise level drops below the ambient noise level. When the current signal noise level drops below the ambient noise level, the system assumes that a three-way conference call has been attempted by the called party.

Claims

1. A method for detecting the initiation, by a called party, of a three-way call, comprising the steps of:

(a) determining a baseline ambient noise level on a telephone line connecting a calling phone to a central office;

(b) monitoring a current ambient noise level on said telephone line, and generating a signal (ON_-- HOLD) indicative of a three-way call when said current ambient noise level falls below a second level which is below said baseline ambient noise level by a predetermined amount, and continuously remains below said second level for a predetermined amount of time.

2. A method as recited in claim 1, wherein said baseline and current ambient noise levels are measured by computing an absolute value of a voltage or current on said telephone line.

3. A method as recited in claim 1, wherein a current or voltage signal on said telephone line is filtered to remove from said current or voltage signal at least frequency components below approximately 300 Hz before said current or voltage signal is employed to determine the baseline and current ambient noise levels on said telephone line.

4. A system for detecting the initiation, by a called party, of a three-way call, comprising:

(a) means for determining a baseline ambient noise level on a telephone line connecting a calling phone to a central office;

(b) means for monitoring a current ambient noise level on said telephone line, and generating a signal (ON_-- HOLD) indicative of a three-way call when said current ambient noise level falls below a second level which is below said baseline ambient noise level by a predetermined amount, and continuously remains below said second level for a predetermined amount of time.

5. A system as recited in claim 4, wherein said baseline and current ambient noise levels are measured by computing an absolute value of a voltage or current on said telephone line.

6. A system as recited in claim 4, comprising means for filtering a current or voltage signal on said telephone line to remove from said current or voltage signal at least frequency components below approximately 300 Hz before said current or voltage signal is employed to determine the baseline and current ambient noise levels on said telephone line.

7. A system as recited in claim 4, wherein said baseline and current ambient noise levels are measured by computing an absolute value of a voltage or current on said telephone line;

and further comprising means for filtering a current or voltage signal on said telephone line to remove from said current or voltage signal at least frequency components below approximately 300 Hz before said current or voltage signal is employed to determine the baseline and current ambient noise levels on said telephone line.