Conference bridge circuit

Claim 2

A conference bridge circuit for establishing substantially uniform transmission communication connections between four-ports of a bridge, said conference bridge comprising: means for arranging said ports of said bridge into pairs, said means including means for connecting the ports of each pair of ports in series; a pair of amplifying means associated with each of said pair of ports; means for interconnecting each said amplifying means of each pair of amplifying means to form a two-wire to four-wire hybrid, said four-wire portion of said hybrid having an input terminal and an output terminal; means for connecting said two-wire portion of each said hybrid to said associated series pair of ports; means for permanently connecting said four-wire portions of each said hybrid together; means for summing signals on the output terminals of said hybrids; and means for distributing said summed signals back to said hybrid input terminals.

Claim 3

The invention set forth in claim 1 wherein said hybrid is a four terminal device, and wherein said series pair of port connecting means includes: a connection from one terminal of a first one of said ports to a first terminal of said hybrid; and a connection from a terminal common to both ports of said series pair of ports to a second terminal of said hybrid, said four-wire portion of said hybrid including an output bus and an input bus, and said four-wire permanent connection means including a connection from said fourth hybrid terminal to said output bus, a connection to said input bus, and a connection from a third hybrid terminal to said input bus.

Claim 4

The invention set forth in claim 2 wherein said amplifiers each have a noninverting positive input terminal, an inverting negative input terminal, and an output terminal, said hybrid further comprising: a connection from said output of a first one of said amplifiers to said first terminal of said hybrid and to said negative terminal of said second amplifier; a connection from said second terminal of said hybrid to said positive terminal of said second amplifier; a connection from said output of said second amplifier to said fourth hybrid terminal and to said negative input terminal of said first operational amplifier; and a connection from said positive input terminal of said first amplifier to said third hybrid terminal.

Claim 5

The invention set forth in claim 3 whereby the gain from said negative terminal of each said amplifier to said amplifier output is a value -n, where n is any positive number, and the gain from said positive terminal of each said amplifier to said amplifier output is a value of + 2n.

Claim 6

A bridge circuit for interconnecting a plurality of two-wire communication devices, said bridge circuit comprising: a plurality of hybrids, each hybrid adapted for converting from two-wire to four-wire operation, said four-wire portion of said bridge including an output bus and an input bus; means for interconnecting said hybrids via said four-wire portion of said bridge, said interconnecting means including a summation means for communicating signals from said output bus to said input bus; and means for connecting each said hybrid to two of said communication devices together in series relationship, each said hybrid including two amplifiers arranged so that the output of each is connected to a first one of the inputs of the other, and further connected so that the output of a first one of said amplifiers at each of said hybrids and a second input to the second one of said amplifiers at each said hybrid are connected to said series combination of said associated communication devices, and said amplifiers at each said hybrid further connected such that said output of said second one of said amplifiers is connected to said output bus and said second input to said first amplifier at each of said hybrids is connected to said input bus.

Claim 7

A bridge circuit for interconnecting a plurality of two-wire communication devices, said bridge circuit comprising: a plurality of hybrids, each hybrid adapted for converting from two-wire to four-wire operation, said four-wire portion of said bridge including an output bus and an input bus; means for interconnecting said hybrids via said four-wire portion of said bridge, said interconnecting means including a summation means for communicating signals from said output bus to said input bus; and means for connecting each said hybrid to two of said communication devices together in series relationship, each said hybrid including two amplifiers arranged so that the output of each is connected to a first one of the inputs of the other, and further connected so that the output of a first one of said amplifiers at each of said hybrids and a second input to the second one of said amplifiers at each said hybrid are connected to said series combination of said associated communication devices, and said amplifiers at each said hybrid further connected such that said output of said second one of said amplifiers is connected to said output bus and said second input to said first amplifier at each of said hybrids is connected to said input bus.

Claim 8

The invention set forth in claim 5 whereby the gain via the direct path from said connection from said output of said second amplifier to said first amplifier output is equal in magnitude and opposite in phase to the gain via the path through said summation means from said output of said second amplifier to said first amplifier output.

Claim 9

The invention set forth in claim 6 whereby the output buses of all said hybrids are connected to said summation means and whereby an output of said summation means is connected to said input buses.

Claim 10

The invention set forth in claim 7 whereby said summation means comprises a passive network of resistors.

Claim 11

The invention set forth in claim 7 whereby said summation means comprises a summing amplifier.

Claim 12

The invention set forth in claim 5 whereby each said hybrid amplifier has associated therewith gain control means and said summation means has associated therewith gain control means so that the gain from one port of any hybrid to the ports associated with all other hybrids can be adjusted to a desired transmission level by adjusting the gains of one or more of said gain control means.