Subscriber's line equipment for a telephone exchange

Claim 2

A subscriber's line equipment for a telephone exchange, comprising: a. a circuit for supplying direct current to the subscriber's line, which comprises: 1. first and second constant direct current sources, wherein: I. the negative terminal of said first source is connected to ground; and Ii. the positive terminal of said second source is connected to ground; 2. a step-up transformer having a ferrite core, with intermediate tapping of the primary winding, and primary winding terminals;

Claim 3

two pulse generators of rectangular pulses each having a duty factor of 0.5 and a repetition radio frequency; 4. a first PNP transistor connected as a current generator, in series with said first current source, wherein: I. the collector of said transistor is connected to the intermediate tapping of said transformer; Ii. the emitter of said transistor is connected, by a first resistor, to the positive terminal of said first source; Iii. the base of said transistor is connected, by a second resistor, to the positive terminal of said first source, and 5. a third resistor, connected between the base of said first transistor and, by a fourth resistor, to the negative terminal of said second source; 6. two NPN transistors having a common emitter connection, wherein; I. the collectors of said transistors are respectively connected to said primary winding terminals of said transformer; Ii. the bases of said transistors are respectively connected to the output of the pulse generators; and Iii. the emitters of said transistors are connected to ground; and

Claim 4

two pulse generators of rectangular pulses each having a duty factor of 0.5 and a repetition radio frequency; 4. a first PNP transistor connected as a current generator, in series with said first current source, wherein: I. the collector of said transistor is connected to the intermediate tapping of said transformer; Ii. the emitter of said transistor is connected, by a first resistor, to the positive terminal of said first source; Iii. the base of said transistor is connected, by a second resistor, to the positive terminal of said first source, and 5. a third resistor, connected between the base of said first transistor and, by a fourth resistor, to the negative terminal of said second source; 6. two NPN transistors having a common emitter connection, wherein; I. the collectors of said transistors are respectively connected to said primary winding terminals of said transformer; Ii. the bases of said transistors are respectively connected to the output of the pulse generators; and Iii. the emitters of said transistors are connected to ground; and

Claim 5

rectifying means connected to the transformer secondary winding for supplying direct current to the subscriber's line; 8. a first filtering capacitor shunting the subscriber's line; and 9. a second high-frequency decoupling capacitor, connected between ground and said intermediate tap of said transformer primary winding; and b. a first circuit for transmitting voice signals from the telephone exchange to the subscriber's line, having an impedance-matching, unit-gain buffer amplifier at its input connected by a fifth resistor to a current generator comprising a first differential amplifier having a negative-feedback loop connected to the base of said first resistor by a sixth resistor, and wherein said third resistor comprises a positive-feedback resistor; c. a second circuit for transmitting voice signals from the subscriber's line to said telephone exchange, comprising a low-pass filter having a seventh resistor and a third capacitor, wherein said seventh resistor is connected between the intermediate tapping of said transformer and the negative input of a second differential amplifier by an eighth resistor in series with a fourth capacitor, whereby said second differential amplifer has a negative feedback loop; d. a ninth resistor, for providing an antiside tone effect, being connected between the output of said buffer amplifier and the connection between said fourth capacitor and said eighth resistor; and e. a tenth resistor, for matching the impedance relative to the telephone line, being connected between the output of said second differential amplifier and the negative input of said first differential amplifier.

Claim 6

rectifying means connected to the transformer secondary winding for supplying direct current to the subscriber's line; 8. a first filtering capacitor shunting the subscriber's line; and 9. a second high-frequency decoupling capacitor, connected between ground and said intermediate tap of said transformer primary winding; and b. a first circuit for transmitting voice signals from the telephone exchange to the subscriber's line, having an impedance-matching, unit-gain buffer amplifier at its input connected by a fifth resistor to a current generator comprising a first differential amplifier having a negative-feedback loop connected to the base of said first resistor by a sixth resistor, and wherein said third resistor comprises a positive-feedback resistor; c. a second circuit for transmitting voice signals from the subscriber's line to said telephone exchange, comprising a low-pass filter having a seventh resistor and a third capacitor, wherein said seventh resistor is connected between the intermediate tapping of said transformer and the negative input of a second differential amplifier by an eighth resistor in series with a fourth capacitor, whereby said second differential amplifer has a negative feedback loop; d. a ninth resistor, for providing an antiside tone effect, being connected between the output of said buffer amplifier and the connection between said fourth capacitor and said eighth resistor; and e. a tenth resistor, for matching the impedance relative to the telephone line, being connected between the output of said second differential amplifier and the negative input of said first differential amplifier.