Abstract: A protection device, for a telephone (or other load) 27 in series with an external protection transistor 2, includes a sensor 6 for detecting common-mode current into the load. The output of the sensor 6 is connected to affect a current source/sink combination, and imbalance in this source/sink combination produces a voltage shift which is indirectly connected to control the protection transistor.

Abstract: A method of measuring under running conditions operation parameters of an interface circuit and a telephone subscriber line connected to it, said interface circuit comprising a first integrated circuit operating on a high voltage with outputs connected to the line and second outputs on which transverse and longitudinal current values of the line are respectively present in normal operation, and a second integrated circuit operating on a low voltage between the first circuit and a telephone exchange, comprises the steps of: switching the outputs across an impedance of a predetermined value, and measuring through the first circuit the values of the currents present on the second outputs; switching said outputs back to across the line leads, and measuring through the first circuit the values of the transverse and longitudinal line current values; performing, for each measurement through the second circuit, a digital encoding of the measured values and transmitting such encoded values to the telephone exchange.

Abstract: 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 effec

Abstract: An integrated circuit bandgap voltage reference, in which the regulated voltage is equal to the sum of a first transistor's base-emitter voltage plus a voltage which is proportional to the difference between the base-emitter voltages of two transistors operating at different current densities, PLUS an additional voltage which is equal to the base-emitter drop of an additional transistor. The additional transistor is connected to an emitter resistor which ensures that variations in resistor values will cause the base-emitter drop of the additional transistor to vary oppositely to the base-emitter drop of the first transistor. The resulting voltage reference circuit has high stability and low power consumption.

Abstract: 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.

Abstract: A vertical, isolated-collector transistor of the pnp type comprises an island doped similarly to the collector region and formed in the surface epitaxial layer of the transistor between that collector region and one of the isolation zones. That island extends in depth to penetrate a similarly doped intermediate region and short out the epitaxial layer included between the isolating layer and the collector region so as to suppress the effects of active parasitic junction components by holding a transistor and a silicon-controlled rectifier of parasitic types, as nesting within the structure of the vertical pnp transistor, in a cut-off state.

Abstract: An interface circuit between a subscriber's telephone line and exchange control components, with a reduced current consumption in the case of a grounded cable, includes a control circuit which senses the increase in the amplitude of the longitudinal currents on the line due to the grounded cable condition and consequently controls the disconnection of the current supplied to the line. However, the line is still supplied periodically for very short periods so as to reduce as far as possible current consumption during the grounded cable condition, but to allow the control circuit to sense the removal of the breakdown and to restore the normal current supplied to the line.

Abstract: 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.

Abstract: 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.

Abstract: A circuit for automatically controlling the gain-bandwidth product of operation amplifiers, where gain-bandwidth product (G*B) of one of the amplifiers placed on the same chip as the amplifiers to be controlled is measured and the resulting signal is used to control through a bias circuit the gain-bandwidth products of all the amplifiers, the value of these products being presettable through the frequency of a control signal sent to the circuit input. The reference amplifier is highly compensated for and placed in the configuration of voltage follower.

Abstract: A Subscriber Line Interface Circuit (SLIC) having a voltage regulator for application thereto of a DC supply voltage V.sub.B and connected at the output terminals to an audio transmission line to provide a line current I.sub.L and voltage V.sub.L for a given resistance load R.sub.L on the line, is provided with a control circuit which, by picking up appropriate current and voltage values from the interface circuit, outputs a voltage value which is the equal of the difference between an optimum supply voltage V.sub.BF and the supply voltage V.sub.B. The control circuit output is connected to the voltage regulator to minimize the voltage V.sub.BFK applied to the interface circuit as the transmission line resistance load R.sub.L varies, thus minimizing the power dissipated through the interface circuit.

Abstract: A telephone circuit, which may be monolithically integrated, for supplying ringing signals to a subscriber's line and for detecting an off the hook condition during ringing includes a circuit for supplying ringing signals coupled to exchange control components for generating a constant frequency sinusoidal signal which gives rise to the ringing signals and an enabling circuit, controlled by the exchange components, for enabling the supplying of the ringing signals to the line and for activating a circuit for detecting a direct current on the line. The circuit for detecting a direct current on the line supplies a signal to a circuit for controlling the detection of an off the hook condition, and which supplies an inhibiting signal for the enabling circuit and check, only after a predetermined time, whether the circuit for detecting a direct current on the line is still supplying a signal and for generating a signal informing the exchange components that the set has been off the hook.

Abstract: A circuit, which may be monolithically integrated, for measuring longitudinal and transverse currents in a two-wire transmission line, includes first and second current mirror circuits of a first type, each having an input branch and first and second output branches. The measuring circuit also includes third, fourth and fifth current mirror circuits, each having an input branch and an output branch, and first and second currents mirror circuits of a second type, each having first and second input branches and first and second output branches. The input branches of the first and second current mirror circuits of the first type and the first input branches of the first and second current mirror circuits of the second type are used as input terminals for coupling to the line.

Abstract: An integrated circuit for the transmission of telephone signals is designed so as to be inserted in a speech circuit of a subscriber's telephone set and includes a threshold comparator having first and second input terminals coupled to the terminals of a two-wire telephone line and an output terminal connected to a point of the signal path of the circuit. The threshold of this comparator is set such that when the voltage at the terminals of the line drops to a predetermined value, which is not lower than the minimum voltage value required to ensure the correct operation of all the components of the circuit, it generates an output signal used to limit the amplitude of the negative peaks of the waveforms of the transmitted signals.

Abstract: The broad-band integrator uses bipolar transistors with single low-value integration capacitor, that is why it is easy to integrate. A bias circuit, which can be integrated, allows both the gain-bandwidth product (G*B) and the absolute values of the currents in the transistors to be programmed by two external resistors. A plurality of integrators, typically sixteen, can be connected to the same bias circuit thanks to their small power consumption.

Abstract: A telephone circuit which may be monolithically integrated for generating control signals for displaying the telephone charges to a subscriber is coupled to an AC voltage signal generator of having a predetermined amplitude and frequency which are constant over time. The circuit includes a voltage generator for generating signals which are spaced over time and have a trapezoidal pulse waveshape. A multiplier circuit calculates the product of the signals supplied from the two voltage generators and supplies a signal which is sent to the speech circuit of the subscriber's line and is added to the speech signals. The trapezoidal pulse generator has a capacitor which is charged and discharged by a voltage to current converter of a non-linear type which is driven by exchange control components. The voltage across this capacitor forms the trapezoidal signals supplied by the generator.

Abstract: 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.

Abstract: A network for supplying identical biasing voltages and programmable direct currents to a plurality of mutually similar transceivers, connected across respective transmission lines, is integrated with the associated transceivers in a common semiconductor body and comprises a generator of fixed reference voltage determined by the band gap of the semiconductor. The reference voltage is applied in parallel to the bases of several NPN transistors emitting the same biasing voltage as a result thereof. This reference voltage also drives an NPN pilot transistor lying in series with an external resistor through which it draws a small programmed current. Through two cascaded amplification stages formed by NPN transistors operating in the ECL mode, with the second stage designed as a multiple-output current mirror, the programmed current is stepped up to provide the several direct currents required by the associated transceivers.

Abstract: A monolithically integratable current adding circuit includes a current mirror circuit, the input port of which forms a first input terminal of an adding circuit and the output port of which is connected, via two series connected resistors, to a voltage reference. The point of connection between these series connected resistors forms a second input terminal of the adding circuit. The adding circuit also includes a voltage to current converter which has a first and second input terminal connected respectively to the output port of the current mirror circuit and to the voltage reference and which has an output terminal which forms the output terminal of the adding circuit.

Abstract: Differential stage comprising a high input dynamic range differential circuit formed by first and second transistors whose emitter electrodes are connected together and to a constant current source through respective resistors, their base electrodes having an input signal applied thereto, and their collector electrodes supplying respective collector currents. The stage further comprises a dual-single converter circuit receiving the collector currents at its input and supplying a stage output current, said converter circuit including at least one variable current source and having a conversion factor which varies as a function of the variable source current.