Sgs-thomson Microelectronics S.r.l.

Sgs Microelettronica Spa

Other

Societe Anonyme De Telecommunications

Sgsates Componenti Elettronici S.p.a.

Vanni Saviotti

Marco Siligoni

Aldo Torazzina

Mauro Pasetti

Ferdinando Lari

Marco Siligoni, Deceased

Emilio Lorena

Jean-Louis Lavoisard

Angelo Pariani

Walter Rossi

Vittorio Comino

Maria L Marcioni

An integrated telephone interface circuit for driving a telephone line includes a line current sensor and a phase converter, both associated with an output stage connected to the telephone line. The circuit is equipped with a protection device against the generation of spurious signals including a comparator connected between the converter and the output stage, a control and monitoring circuit linked operatively to an output of the comparator, and a plurality of switches associated with the input side of the converter, as well as with the current sensor and the output stage. The switches are linked operatively to respective outputs of the control and monitoring circuit to reverse polarity of the line supply upon a predetermined threshold value for the comparator being exceeded.

Integrated interface circuit for driving a subscriber line

A circuit for limiting power dissipation through telephone subscriber line power supply interface devices, by using a pair of final stages to which an external component effective to dissipate power is connected. By use of separate discrete reference circuits, the presence of excessive common mode current is detected; and when this occurs, current to the driver stages is controlled at a lower magnitude.

Power dissipation manager circuit for an interface device feeding a

A circuit assembly which includes an interface circuit between a subscriber line and exchange devices of the kind with two amplifiers connected in a bridge configuration between the battery terminals and having a means of detecting the output currents; a supply circuit which includes the exchange battery and a ring generator; a switch-over means for putting the line through the interface circuit or the supply circuit; two bridge resistors which are in series with the line when the latter is connected to the supply circuit and of which one is connected permanently between one of the line terminals and the output of one of the amplifiers, which output is substantially at the potential of one of the battery poles; an additional resistor, having a much higher resistive value than that of the bridge resistors and being connected between the other of the line terminals and the output of the other of the amplifiers; and a processing means within the interface circuit, which includes said detecting means and is effective to isolate the useful signal from the line current, recognize a possible hook-off state, and send a corresponding signal to the exchange devices.

Telephone circuit assembly

An electronic interface circuit between a telephone subscriber line and a telephone main exchange is disclosed which forms, with the main exchange battery, a supply bridge for the telephone line, with limitation of the line current to a predetermined threshold value. The voltage/current characteristic of the supply bridge is balanced for lower values of the line current than the threshold current and is unbalanced whenever the line current attains said threshold current.

Current limited subscriber interface circuit

A method of lowering the power absorbed by an interface circuit, in the 'power-down' state thereof, as incorporated to a telephone exchange and connected to a telephone subscriber line, being of a type which comprises a monitoring circuit portion connected between the line and the exchange. The method involves the steps of,

Subscriber line interface circuit with power-down mode

A telephone circuit, which may be monolithically integrated, for supplying ringing signals to a subscriber's telephone line and for detecting an off the hook condition during ringing, including a logic control circuit connected to exchange components which control the supply of the ringing signals and determine their rhythm. The logic control circuit is connected to a circuit for detecting direct current on the line and a current comparator for generating a signal when the value of the line current exceeds a predetermined current value. This signal is also supplied to the exchange components via a transfer circuit to inform them that an off the hook condition has taken place. The logic control circuit is connected to a timing signal generator which synchronizes its functions with times in which the ringing signal has a zero amplitude, and is connected to a signal amplifier circuit which supplies the ringing signals to the line and to the transfer circuit. When the circuit for the detection of direct current signals a probable off the hook condition, the logic control circuit disables the amplifier circuit from supplying ringing signals to the line and inhibits the transfer of any signals to the exchange components, and checks after a predetermined time interval that an off the hook condition has actually taken place.

Monolithically integratable telephone circuit for supplying ringing

A telephone circuit, which may be monolithically integrated, for feeding a subscriber's telephone line which is coupled via the circuit to a supply voltage generator. The circuit supplies the line with an impedance having a first predetermined value up to a given value of the line current, beyond which is supplies the line with an impedance of a second value greater than the first. The circuit is electrically equivalent to a voltage generator, identical to the supply voltage generator, having circuit components solely of the resistive type connected in series therewith.

Monolithically integratable telephone circuit for feeding a subscriber's

A telephone circuit for ring trip detection that can be monolithically integrated, includes a current transducer coupled to a user's telephone line, and an integrator circuit. The output current of the current transducer is proportional to the line current until equal and opposite threshold values are reached. When the line current threshold values are exceeded, the transducer output current is constant. The transducer output current is integrated by the integrator circuit over at least one complete cycle. When a telephone headset is removed, a direct current is applied to the ringing signal current resulting in asymmetry in the half-cycles of the transducer output current. The asymmetry provides a non-zero integrated current for a complete cycle. When the integrated value of the asymmetrical current is greater than a selected value, a signal is applied to the ringing circuit, halting the ringing signal.

Method and apparatus for an improved ring trip detection telephone

A telephone circuit which may be monolithically integrated, for generating control signals for displaying the telephone charges to a telephone user, is coupled to a AC voltage signal generator having a predetermined amplitude and frequency which are constant over time. The circuit includes a voltage generator for generating voltage signals which are spaced over time and have a trapezoidal pulse waveshape. A multiplier circuit calculates the product of the signals supplied by the two generators and supplies a signal which is sent to the speech circuit of the subscriber's line and is added to the speech (i.e.--conversation) signals. The circuit also includes a circuit for receiving an image signal of the overall signal adapted to the telephone line; a high-pass filter for eliminating the speech signal components from the image signal; a rectifier circuit for rectifying the filtered signal and a comparator for comparing the rectified signal with a reference signal. If the amplitude of the rectified signal is greater than the amplitude of the reference signal, the comparator generates a signal designed to stop the increase in the level of the trapezoidal pulse signals generated by the voltage generator thereby regulating the amplitude of the trapezoidal pulse signals.

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Monza, Italy

Vanni Saviotti