The present invention relates to a method for establishing a telephone conference in a telephone system, and more particularly, to a method of combining voice signals so that a telephone conference may include hundreds of members and so that a member may participate in more than one conference.
Typically, telephone systems include some form of digital timeshare circuitry to communicate voice signals among users. In such systems, the voice signals are digitized and are routed by a central processor to the intended recipient. (The term "voice signal(s)" also refers to other analog signals that may be digitized and communicated, such as analog data signals.) Where more than one such digital signal is to be routed to a single recipient, as in a conference, the digital signals are typically added. The digital signals may be received and added in a first timeframe and the sum transmitted during a second timeframe. The present invention relates to the method of summing the digital signals.
While various methods of combining digital signals for a telephone conference are known, none provide the versatility that allow use of the method with a small conference of only a few members and with a conference of hundreds of members without changing telephone system hardware. Further, none of the known methods can also allow a member of one conference to simultaneously monitor other conferences.
It is known, for example, to combine digital signals in a telephone conferencing circuit by using a pyramid of additions. In such methods the sum of two signals is added to another signal, with the sum being added to a further signal, and so on until all signals are added. For a system with hundreds of signals the result may require hundreds of levels of additions and a complex mapping scheme to provide the signals to the right spots in the pyramid. Such a pyramid arrangement may degrade the signal and may provide problems with time sequencing of signals in the telephone system. See, for example, the system in U.S. Pat. No. 4,975,902 to Damany.
Other methods for combining signals in a telephone conference may require additional access lines or other hardware to accommodate conferences with hundreds of members. See, for example, U.S. Pat. No. 4,481,624 to Baranyai, et al., U.S. Pat. No. 3,997,730 to Stidham and U.S. Pat. No. 3,971,895 to Hollis, et al.
The method of the present invention uses a multiplicity of identical adders and a repeatable hierarchical scheme to provide the flexibility needed for both large and multiple conference capabilities. In a preferred embodiment of the present invention, groups of up to six conference members are formed and digital signals from each of the six members are provided to a first adder where all six signals are combined. Through six additional adders, each member of the group receives signals from every other member of the group. When more than one group of six is present, the combined signals from all of the first adders from the groups are combined in a second adder. Through additional adders, each group receives the combined signal from every other group. This hierarchical scheme may be repeated until all groups of six members are combined and every group receives signals from every other group.
Accordingly, it is an object of the present invention to provide a novel method of combining digital signals for a telephone conference that is versatile enough to operate with large and small conferences and which obviates the problems of the prior art.
It is a further object of the present invention to provide a novel method for telephone conferencing that uses a plurality of identical adders arrayed in a repeatable hierarchical scheme.
It is yet a further object of the present invention to provide a novel method of combining signals for a telephone conference in which the same hardware may be used to provide conferences with sizes ranging up to hundreds of members and to provide the capability to combine conferences.
It is another object of the present invention to provide a novel method of combining signals for a telephone conference in which a member of one conference may monitor a second conference without rearranging or otherwise affecting the first conference.
These and many other objects and advantages will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of preferred embodiments.