Telephone antisidetone circuit

Claim 2

For limiting sidetone in a telephone set, a three-port circulator, wherein each port is defined by a pair selected from the three terminals of a circuit using two amplifiers, each amplifier having a pair of input and a pair of output terminals which amplifiers provide phase changes between input and output differing from each other by approximately 180*, wherein said three terminals are defined as follows: a. a connection to one input and one output terminal of each amplifier; b. the connection of the other input terminal from one amplifier and the other output terminal from the other amplifier; and c. the connection of the other output terminal from sad one amplifier and the other input terminal from said other amplifier; wherein a telephone line, telephone receiver and mouthpiece are connected in that cyclical order to the ports whose corresponding cyclical order is arranged to circulate power in said cyclical order.

Claim 3

Circuitry as claimed in claim 1 wherein the phase change contributed by said one amplifier is between 0*-70* phase advance over the frequency range 200 to 6,000 Hz. and the phase contributed by said other amplifier is between 180* and 250* phase advance and the direction of circulation of power in said amplifier is cyclically a-c, c-b, b-a.

Claim 4

Three-port transistorized circulator using wires for connecting circuit elements for limiting sidetone in a telephone set designed for the sense of power circulation wherein power input at a port provides much greater output at the next following port, in the cyclical sense of rotation, then the power output at the next preceding port; wherein a telephone line is connected across one of said ports; a telephone receiver is connected across the next port in the cyclical sense of power circulation; and a telephone mouthpiece is connected across the third port in the sense of power circulation, wherein said circulator comprises a pair of amplifiers, each amplifier having two input terminals and two output terminals with one input terminal being connected to one output terminal and with this connection being connected to the corresponding connection for the other amplifier, and, in the case of each amplifier, the other input terminal thereof being connected to the other outlet terminal of the other amplifier, said amplifiers being designed so that the phase change in one amplifier, between input and output, differs from the corresponding phase change in the other amplifier by approximately 180*, where the three said ports are defined by: a. the connection between the connected input and output terminals of the two amplifiers; b. one connection between the other input terminal of one amplifier and the other output terminal of the other amplifier, c. the other connection between the other input terminal of the other amplifier and the other output terminal of the one amplifier.

Claim 5

Three-port transistorized circulator using wires for connecting circuit elements for limiting sidetone in a telephone set designed for the sense of power circulation wherein power input at a port provides much greater output at the next following port, in the cyclical sense of rotation, then the power output at the next preceding port; wherein a telephone line is connected across one of said ports; a telephone receiver is connected across the next port in the cyclical sense of power circulation; and a telephone mouthpiece is connected across the third port in the sense of power circulation, wherein said circulator comprises a pair of amplifiers, each amplifier having two input terminals and two output terminals with one input terminal being connected to one output terminal and with this connection being connected to the corresponding connection for the other amplifier, and, in the case of each amplifier, the other input terminal thereof being connected to the other outlet terminal of the other amplifier, said amplifiers being designed so that the phase change in one amplifier, between input and output, differs from the corresponding phase change in the other amplifier by approximately 180*, where the three said ports are defined by: a. the connection between the connected input and output terminals of the two amplifiers; b. one connection between the other input terminal of one amplifier and the other output terminal of the other amplifier, c. the other connection between the other input terminal of the other amplifier and the other output terminal of the one amplifier.