Six-port conference amplifier circuit

Claim 2

A telephone conference amplifier circuit comprising six coupling means each one of which is associated with an external port, all of said coupling means internally connected in a hexagonal ring, three pairs of substantially equal value resistors, each said pair being respectively connected to the coupling means of adjacent pairs of ports to form three balanced bridge circuits, a differential amplifier means connected to each bridge circuit for detecting and amplifying signals originating in that bridge, and means for coupling the output of each amplifier means to the common point between the other two bridges, thus coupling a signal from one port into the other ports of the amplifier.

Claim 3

A telephone conference amplifier circuit according to claim 1 wherein each of said coupling means is a transformer device having a primary winding connected to one of said external ports and a secondary winding serially connected in said hexagonal ring.

Claim 4

A telephone conference amplifier circuit comprising a plurality of coupling networks each having primary and secondary circuits, each of said primary circuits associated with a port, said secondary circuits all being connected in a series circuit such that a hexagonal ring is formed by said secondary circuits; and a plurality of resistive means each having first, second and third terminals, said first terminal connected to one of the outer terminals of a pair of adjacent secondary circuits and said third terminal connected to the other outer terminal of said pair of adjacent secondary circuits such that three bridge circuits are formed each comprising an adjacent pair of secondary circuits and one of said resistive means; and each of said bridge circuits further including amplifying means having two input terminals and a single output terminal, one of the input terminals of said amplifying means connected to the common node connecting the inner terminals of the adjacent pair of secondary circuits in that bridge circuit and the other input terminal of said amplifying means connected to the second terminal of the resistive means having first and third terminals connected to the outer terminals of the adjacent pair of secondary circuits in the same bridge circuit, and the output terminal of said amplifying means connected to the common node connecting the other two bridge circuits such that each primary circuit is coupled to all the other primary circuits.

Claim 5

A telephone conference amplifier circuit comprising a plurality of coupling networks each having primary and secondary circuits, each of said primary circuits associated with a port, said secondary circuits all being connected in a series circuit such that a hexagonal ring is formed by said secondary circuits; and a plurality of resistive means each having first, second and third terminals, said first terminal connected to one of the outer terminals of a pair of adjacent secondary circuits and said third terminal connected to the other outer terminal of said pair of adjacent secondary circuits such that three bridge circuits are formed each comprising an adjacent pair of secondary circuits and one of said resistive means; and each of said bridge circuits further including amplifying means having two input terminals and a single output terminal, one of the input terminals of said amplifying means connected to the common node connecting the inner terminals of the adjacent pair of secondary circuits in that bridge circuit and the other input terminal of said amplifying means connected to the second terminal of the resistive means having first and third terminals connected to the outer terminals of the adjacent pair of secondary circuits in the same bridge circuit, and the output terminal of said amplifying means connected to the common node connecting the other two bridge circuits such that each primary circuit is coupled to all the other primary circuits.

Claim 6

A telephone conference amplifier circuit according to claim 3 wherein each of said coupling networks is a transformer device.

Claim 7

A telephone conference amplifier circuit according to claim 4 wherein each of said amplifying means is a differential amplifier and the one of said input terminals is a noninverting input while the other of said input terminals is an inverting input in relation to the phase of the output of each differential amplifier.

Claim 8

A telephone conference amplifier circuit according to claim 5 wherein each of said differential amplifiers has a high input impedance, a low output impedanace, and a gain of two.