Telephone speech network

Claim 2

A telephone speech network, for connecting a transmitter and a receiver to a line powered telephone line, comprising: a first amplifier, the output of which is connected in series with a line terminating resistance across the telephone line, the input to said amplifier being responsive to both the received signals on the telephone line and to the signals at the output of the transmitter; a bridging resistance and a bridging impedance connected in series across said amplifier, for summing substantially equal magnitude receive signal currents and for subtracting substantially equal magnitude transmit signal currents, coupled from the output of the amplifier and from across the telephone line to the junction of said bridging resistance and impedance; and a second amplifier means for connecting the resultant signals at said junction to said receiver.

Claim 3

A telephone speech network, for connecting a transmitter and a receiver to a line powered telephone line, comprising: an output transistor having its collector connected to one side of the telephone line and its emitter connected in series with a line terminating resistor to the other side of the telephone line; means for connecting the transmitter between the base of the output transistor and said other side of the telephone line; a feedback resistor connected between said one side of the telephone line and said base; a bridging impedance and a bridging resistance serially connected between said one side of the telephone line and said emitter for summing substantially equal magnitude receive signal currents and for subtracting substantially equal magnitude transmit signal currents coupled from the emitter and from the telephone line to the junction of said bridging resistance and impedance; signal amplifier means for connecting the resultant signals at said junction to one end of a receiver terminating resistor, the other end of said receiver terminating resistor being connected to said one side of the telephone line; and power amplifier means for connecting the signal across said receiver terminating resistor to said receiver.

Claim 4

A telephone speech network, for connecting a transmitter and a receiver to a line powered telephone line, comprising: an output transistor having its collector connected to one side of the telephone line and its emitter connected in series with a line terminating resistor to the other side of the telephone line; means for connecting the transmitter between the base of the output transistor and said other side of the telephone line; a feedback resistor connected between said one side of the telephone line and said base; a bridging impedance and a bridging resistance serially connected between said one side of the telephone line and said emitter for summing substantially equal magnitude receive signal currents and for subtracting substantially equal magnitude transmit signal currents coupled from the emitter and from the telephone line to the junction of said bridging resistance and impedance; signal amplifier means for connecting the resultant signals at said junction to one end of a receiver terminating resistor, the other end of said receiver terminating resistor being connected to said one side of the telephone line; and power amplifier means for connecting the signal across said receiver terminating resistor to said receiver.

Claim 5

A telephone speech network as defined in claim 2 in which the power amplifier means comprises a differential amplifier having one input connected to the inverted output of said signal amplifier means and the other input connected to said one side of the telephone line, and the receiver being connected between the differential outputs of said differential amplifier.

Claim 6

A telephone speech network as defined in claim 2 in which the means for connecting the transmitter includes a voltage-controlled current amplifier which comprises: first, second and third transistors, the emitters of which are connected to said other side of the telephone line, the collector of the first transistor being connected to the base of the third transistor, the base and collector of the second transistor being connected together and to the base of the third transistor and the collector of the third transistor being coupled to the base of said output transistor; a source of d-c voltage derived from across the line powered telephone line; first and second resistors serially connected between said d-c source and said base of the third transistor, the base of the first transistor being connected to the junction of the first and second resistors; and a third resistor coupled between the transmitter and the base of the third transistor; whereby the magnitude of the transmit signal at the collector of the third transistor varies inversely as the d-c voltage from said source.