JPS62115954A - Digital conference bridge - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] This invention relates to conference bridges.

A telephone network designed to allow multiple interconnections between a large number of communication devices and a large number of telephone sets for the purpose of allowing users to conduct conferences in which each party speaks and listens as needed. Various capabilities occur in communication networks, such as when interconnected. In principle, without considering practical transmission limitations, the condition that if the telephones are analog devices with two-wire links between them, then the interconnection path between the telephones is also a two-wire link. in,
It is possible to connect multiple telephones together for conference type calls. However, where a four-wire link is used where the signals are digitally encoded at some point in the communication circuit, the equivalent technique of direct multiplex interconnection is not possible in the way that intelligible communication allows. Apparatus should be made to switch the large and small signals from each telephone in a manner that directs the signal between telephones.

In order to separate large and small signals from each two-wire telephone link, a hybrid is used to convert the two-wire link to a four-wire link. By digitizing the high signal from each of the telephones and using a suitable switch, block outgoing calls from all but a selected one of the telephones from reaching the rest, while the high signal is selected. It is known to turn from the phone to the rest.

Various means have been proposed for controlling such switches. U.S. Patent Nos. 3.958.084 and 3.947.
No. 639 describes an apparatus for determining which telephone is to be selected for the time being, such that the resulting signal to the remaining telephones is greater than the last selected telephone by the magnitude of the signal from the remaining telephones. It specifies that this is done by comparing the instantaneous magnitudes of the signals, and then operates to replace the dominant selection with another when a certain condition is met. More specifically, if the instantaneous magnitude of the non-selection signal is greater than the corresponding instantaneous magnitude of the signal from the dominant selection, and if that greater instantaneous magnitude is also greater than a predetermined threshold; , the condition exists.

In the devices of these patents, devices are provided for changing the threshold under certain conditions.

More specifically, this threshold is determined to be representative of the peak amplitude of the signal from the selected telephone, but if a new sample of the selected signal falls below the previous threshold. Then, the treatment becomes a stepwise reduction of the threshold. In this way, if the selected signal output fails to reach the threshold level for successive sampling intervals, this threshold will eventually be 0 state will be reached. This means that it is relatively more difficult for the chosen signal to be replaced if the other signal is a larger magnitude signal but can reverberate at its local hybrid; , has the effect of still allowing a relatively free transition to another selected signal if the previously selected signal falls, for example, to O at an acceptable interval.

However, as mentioned above, difficulties arise in implementing a device called a conference bridge, where the signal level from each of the telephones is connected to a bridge with equal signal levels for equal acoustic input to each telephone. will not reach it. This phenomenon occurs when there are differences in the links interconnecting telephones with bridges, for example due to different line lengths or line characteristics. It will be appreciated that in this case, as long as adjustments are made to the signal level, improper operation will occur. This is because a signal from a particular phone exhibiting a greater signal level than signal levels from other phones will tend to take precedence even if this is not needed.

An object of the present invention is to at least partially alleviate the above-mentioned difficulties.

According to one form of the invention, a digital conference bridge is provided by which the output signals from a plurality of communication devices can be controlled, and the output signal from a selected one of the devices is directed to the remaining ones and for the time being. a digital conference such that the selected signal is determined by a selection means in combination with said bridge and at least time-spaced digitized received samples representative of said signal; The bridge has the following characteristics: That is, the above selection means is a first generation means for generating the product xn.gn+X+.gi, where xn and (where gn and gi are predetermined gain factors for all signals and the selected signal, respectively) and a first storage means for storing a threshold value "T". -g, with the product xi. a condition x for controlling said switching means to replace the current selection of said signals by one of said signals with a newly selected signal;
A control means responsive to n·gn>X+·gi and ×ゎ·g,>T−gi.

In this apparatus, the selection means includes updating means for updating said first storage means, said means for comparing said threshold value T currently stored in said threshold register with the product X+'gi. said updating means include second comparator means and means for replacing the current threshold by a new value equal to Xi·gi if the product X+'gi must exceed the current threshold; , the threshold value T is one or more consecutive products xi
- further comprising reduction means coupled to said comparator for reducing said threshold T by a predetermined amount if gi has to be exceeded;

The invention will be further explained by way of example with reference to the drawings.

FIG. 1 shows a telephone footer-up device intended for use in conjunction with a conference bridge constructed in accordance with the present invention.

In FIG. 1, two telephones designated #l and #n as shown are each the first of a series of such telephones.
th and nth telephones, and members between the series of telephones have been omitted for simplicity. Each telephone #1 to #n has each hybrid 20 connection. Each hybrid 20 has a 2-wire link 2 for each phone.
2, an output port coupled to an output line 24 for directing small signals from the hybrid onto line 22, and a large signal line for receiving large signals and directing each from the hybrid onto line 22. It has 26. Line 24°26 related to Hybrid 20
are connected to each digital encoder/decoder device 28. The device 28 operates at a high sampling rate, such as 3 kt (z).
．． It is connected to 32. Highway 30 conveys pulse code modulated time division multiplexed signals therefrom from encoder/decoder device 28 and is connected via gain control device 37 to series-parallel buffer 34 . Highway 32 receives time division multiplexed pulse encoded modulated signals from parallel-serial buffer 36 in the direction of encoder/decoder device 28 . In accordance with the convention of pulse-coded modulated time 0 submultiplex communication systems, the encoder/decoder system 28 is connected to each telephone 18 and the hybrid 20
and forming each time frame for each set of windows corresponding to a set of digitized signals for data transmission on Highway 30. The hybrid 20 receives and decodes the respective correspondingly located signals on the highway 32 by appropriately arranging them in a time window.
and directs it to a suitable one of the telephones 18.

Gain control device 37 outputs the digitized multiplied sample signal X. and a predetermined gain factor g for each of the telephones 18. Therefore, the gain factor is for each signal X. They seem to be different about each other. The device uses the product X for a constant sound level of each telephone set 18 prepared by the caller. - comprises digital multipliers which are suitably programmed so that g, . There will of course be a set of products xn.gn for each set of digitized sample signals from telephone 18.

Buffers 34, 36 and device 37 form part of a conference bridge which further includes elements such as those shown in FIGS.

FIG. 2 shows a register 40 for storing the product xi·gi, which product corresponds to a predetermined one of the set of products xn'gn. The register 40 is updated each time a new set of signals representing the product x 7·gn is received, from which the output signal is directed to the particular telephone 18 which has been selected for the time being as the one telephone to be directed to all remaining telephones. The signal "l" is chosen such that it has the corresponding product xn·gn stored therein as determined by . Thus, for example, if phone #3 is to be selected as such, "l" would have the value 3.

The value of "i" for the previous set of products xn.go is stored in register 60. The product of the new set x 7 g.

is received, it is the product Xt''gi from the set that is stored in register 40, where the value of ``l'' is the dominant value from the selection made from the previous set of products. .

The currently stored value Xi'gi in register 40 is applied to one input of comparator 42, the other input of which receives a signal representing the product x7.g. Comparator 42
is operable to compare the currently stored product Xt"g'+ of the product xn.gn at 40 with the current set of products xn.gn. The comparator 42 is connected to an AND gate 44. It has that output.

FIG. 2 also shows a threshold register 48 having a threshold value "T" stored therein. gain adjustment device 5 (such as a register 48 and a gain lookup table);
0 and the output therefrom is connected to one input of the second comparator 520. The other output of comparator 52 is the product x
7.g, is received. The comparator 52 calculates the product T-g, and x7.
It operates to compare go, where T is the accumulated value of register 48. The output from comparator 52 is coupled to AND gate 44.

The output from comparator 42 is the product x. -g, , is register 4
The output of comparator 42 will be enabled if a condition is to be indicated that is greater than the product stored at zero times 1·gi. Similarly, the product ×. −g, , is the product derived from the threshold register and gain lookup table 50;
If r-gi is greater than then the output of comparator 52 will be enabled. If the outputs of both comparators 42 and 52 should be enabled, the output from gate 44 is enabled. Gate 44 has its output connected to register 60 to store the value of "i", the identification of the particular telephone from which the signal is to be directed to the remaining telephones for the time being. The enable of the output of gate 44 is ``l'' derived from the corresponding set of products xn·gn.
'' results in an update of register 60 to record the identity of . Register 60 can identify the selected telephone based on the enablement of the output of gate 44 that will occur during the associated PCM frame indicating the particular telephone. Register 40 is register 6
0, so that register 40 can be conditioned such that each frame stores the selected product xi·gi as described above.

The entire update function described above with respect to register 60 is performed under the control of microprocessor 65, which microprocessor implements the product Kn'g to the circuit of FIG.
The output of n would also be used.

The actual switching of signals between telephones 18 is performed once the
'' is executed by the microprocessor 65, which is coupled to the register 60 and also controls for the direction of signals from the telephone identified by the last selection of "l" to the remaining telephones. It is also coupled to buffers 34, 36 which act as regular switches. More particularly, microprocessor 65 is coupled to bus 80, to which buffers 34, 36 are similarly connected for transferring signals between the buffers under control of the microprocessor.

In FIG. 3, which shows another part of the bridge, means for updating register 48 are shown. here,
Register 48 is shown connected to a tristate 78 which is capable of outputting the value T stored in register 48 as requested on data bus 80. , bus 80 communicates with, among other things, device 50. Register 40 is also shown in conjunction with comparator 66 which receives the output from register 48 and the output from register 40. Comparator 66
is the threshold value T stored in register 48 and register 4
One output 66a of comparator 66 is enabled if it is less than or equal to the last accumulated product times 1·gi. This output is connected to a three-state device 70 and arranged so that the three-state device 70 is enabled in this condition. Three-state machine 70 is coupled to register 40 and, when enabled, it reads (from register 40) the product xi·gi
to output line 70a, and from there to data bus 80.
give to Bus 80 comprises a connection to microprocessor 65, which updates register 48 by substituting the product x1.gi so output for the previous threshold T.

Bonds X+'g where a pre-existing threshold value T has been accumulated
If t is exceeded, output 66b of comparator 66 is enabled. This output is connected to one input of each of two AND gates 74 and 90. The other input of gate 74 is connected to the output of counter 76. gate 90
The other input of is connected to the output of counter 76 via inverter 89. The inputs of counter 76 are selectively coupled to threshold register 48 and register 90 in a manner to be described below. When a carryover of the contents of counter 76 occurs, the output from the counter is enabled;
and upon simultaneous enable of output 66b, gate 7
4 is enabled and gate 90 is not enabled. Enabling gate 74 disables a three-state device and enables another three-state device 64.

Tristate device 64 is then connected from the output of register 48 through table lookup device 51 to bus 80.

The device 51 causes a digital signal applied thereto representing the threshold value T stored in the register 48 to decrease the value represented thereby (e.g. by a digital "i") and generate a new lower value. The system is arranged to operate such that a threshold value T is generated. microprocessor 65
The action of causes the new value to replace the previously existing value in the register.

However, under the condition that output 66a of comparator 66 is enabled, counter 76 may not overflow. In this case, gate 74 is disabled and gate 90 is enabled. Tri-state device 64 is then disabled and tri-state device 78 is enabled to allow the output from register 48 to reach bus 80. In this case, microprocessor 85 reads the threshold value stored in register 48 for direct transfer to bus 80. In this way, PCM every time
A new frame of the signal is processed and the threshold held in register 48 is updated by replacing its value with a new value Xi·gi representing the new higher threshold, or if the condition T < Xi· If gi dominates, the current threshold is either maintained (if cloud counter 76 does not overflow) or decreased (if counter 76 overflows). However, the look-up daple device is preferably configured such that no reduction in the threshold occurs once the O value is reached.

Counter 76 is provided in view of the following fact.

That is, the threshold value stored in register 48 is normally 7.
is a bit eight-law encoded PCM signal, and if it were to act directly to effect a decrease in the value of ITJ in register 48, an undesirable step would occur in the decrease of the threshold in the register. In use, counter 76 is preloaded to a predetermined count less than its full capacity.

The outputs of tristate devices 81 and 82 are coupled to a lookup table 83 on a common input bus 84. Output 66
If b is enabled (ie if T>Xt-gt), then the three-state machine is enabled. When output 66a is enabled (i.e., if T x 1·g)
, three-state device 82 is enabled. Counter 76 will continue to operate as long as output 66a is enabled (i.e., T
<Xi・gi) or is preloaded with the output of lookup table 83 (its output is then
conditioned in a predetermined manner according to the value "T" stored in register 48), or the counter overflows. The input of tri-state device 82 is connected to register 40 and the enable of tri-state device 82 is
It is effective to increment the count in counter 76 in a manner proportional to the value Xt'gi, where it is stored in register 40. In this manner, the number of enable outputs 66b required to produce an overflow from counter 76 depends on the magnitude of the stored values in registers 48 and 40. In this perspective, lookup table 83
may be configured to enable preloading of counter 76 with a value that is in one aspect inversely proportional to the value of "T" represented therein. Since the output of the counter is then only enabled on an overflow condition, the time required for the decrease in the accumulated threshold to occur is correspondingly proportional to the magnitude of the accumulated threshold. Similarly, each increment of the counter from register 40 via tristate device 82 is made by a value that is inversely proportional in some manner to each Xi'gm value provided to lookup table 83.

The operation of the bridge can be described by the following algorithm written in Pascal. That is, i:=In5
tant 5peaker; For n: = l t
o Number of conferences d.

If (Xn”Gn >XioGi) AND (Xn
“Gn>Threshold” Gn) then l
: =n; (1) If Xi” Gi>Threshold Then
threshold :=ABS(Xi”Gi); If Threshold>Q ThenThres
hold: = Threshold −1; For
n : = l to Number of con
ferees d.

If n<> i Then Yn:
= Xi”Gi;In5tant 5peaker:
=i; The above-described apparatus is proposed for illustration only and many modifications may be made without departing from the spirit and scope of the invention as defined in the claims.

[Brief explanation of drawings]

FIG. 1 shows the interconnection of telephones to a conference network by means of an encoding device for buffers. FIG. 2 is a diagram of a portion of a conference bridge constructed in accordance with the present invention. FIG. 3 is a circuit diagram of another portion of a conference bridge constructed in accordance with the present invention. 18...Telephone 20...Little Ibrid 2
2...2 line link 24...Outgoing line 26...
Large signal line 28...Digital encoder/decoder device 30, 32...
...PCM highway 34...Series-parallel buffer 36...Parallel-serial buffer 37...Gain control device 4o...Register 4
2...Comparator 44...And gate 4
8...Threshold register 50...Gain adjustment device (or gain lookup
Table) 51... Lookup table device 52... Comparator 60... Identification register 64... Three-state device 65... Microprocessor 66...
・Comparator 66a, 66b...Output cuff 0
...Three-state device 70a...Output line 74...
- AND gate 76... Counter 78... 3-state device 80... Data bus 81, 82... 3-state device 83... Lookup table 84... Common input bus 85... Micro Processor 89... Inverter 90... AND gate FIG, 2

Claims (1)

[Claims] 1. A digital conference bridge, by which output signals from a plurality of communication devices (#1...#n) can be controlled, and the output signal from a selected one of the devices can be controlled. The signal directed to the remainder and so selected for the time being is determined by a selection means integral with said bridge and with temporally spaced digitized received samples representative of at least said signal. In the digital conference bridge, the above selection means are the products x_n・g_n, x_i・g_
a first generating means (28, 37) for generating i, where x
_n and x_i are the instantaneous sample magnitudes of all signals and the selected signal, respectively, g_n and g_i are the predetermined gain factors for all signals and the selected signal, and the threshold first storage means (48) for storing "T"; and first comparator means (42) for comparing the product x_n·g_n with the product x_i·g_i selected by each non-selected communication device. switch means (65) for routing the signal and for replacing the current selection of said signal with a newly selected signal by one of the previously unselected signals meeting the above conditions; switch means (
65) Conditions for controlling x_n・g_n>x_i・g_i
and control means (44, 52) responsive to x_n.g_n>T.g_n. 2. It includes an update means for updating the first accumulation means (48), and the update means multiplies the threshold value T currently accumulated in the first accumulation means (48) by x_i.
second comparator means (66) for comparing with g_i and for replacing the current threshold by a new value equal to x_i·g_i only if the product x_i·g_i must exceed the current threshold; means (70) for updating said threshold T by a predetermined amount if said threshold T must exceed one or more consecutive products x_i·g_i; said second comparator means (66) to reduce by
A digital conference bridge according to claim 1, further comprising reduction means (51) coupled to. 3. said reducing means (51) operate under the control of a counter (76), said means (83) being provided for preloading said counter with at least a value derived from said threshold T; and means (82) are provided for decrementing the counter (51) if the threshold value is found to exceed the product x_i·g_i, so that the overflow of the counter (76) is 1 one or many consecutive products x_i・g_i
occurs after T has been exceeded by the threshold T, and the counter (76) is stored in the first storage means when the counter (76) overflows.
A digital conference bridge according to claim 2, wherein the digital conference bridge is coupled to means (64) for modifying. 4. Claims 1, 2 or 3, wherein said first generating means comprises a gain adjustment device (37) coupled to receive said digitized signal samples. Digital conference bridge as described in Section. 5. The control means (44, 52) as described above has its input coupled to the output of the first storage means for producing the product T·g_n at the output of the gain lookup table (50). - includes a table (50), the control comparator (52) includes a gain lookup table (
the gate means (44) having inputs coupled to receive the output of the first comparator means (42) and for receiving the product x_n·g_n, respectively;
and an input coupled to receive the output of said first comparator means (42) and said control comparator (52);
The outputs of 2) are x_n・g_n>x_i・g_i, respectively.
and x_n·g_n>T·g_n, and the gating means (44) is enabled if both of these outputs are enabled, but otherwise the gating means (44) , the value 'i' when the gate is enabled
5. A digital conference bridge according to any one of claims 1 to 4, coupled to an identification register (60) for storing ``. 6. The above switch means (65) has an identification register (6
said control means (44
, 52).