Abstract: Low voltage and low power circuits for use in a subscriber power controller includes a low voltage detection circuit for generating a first output signal switching between ECL logic levels and a low power detection circuit for generating a second output signal switching between a high voltage level and a low voltage level. The low voltage detection circuit is formed of a first comparator with hysteresis and a first output stage. The low power detection circuit is formed of a second comparator with hysteresis and a second output stage. The first output signal is used to disable the controller upon detection of a low voltage at the primary input signal voltage. The second output signal is used to inform a microprocessor so as to permit it to disable all high power functions in order to conserve power.

Abstract: A quadruple voltage regulator has four independently controllable power circuits in a single integrated circuit, and includes a current sensor for each of the power circuits. Each current sensor generates an active output signal when the magnitude of the current produced by the corresponding voltage regulator exceeds a selected limit. A single temperature sensing device monitors the temperature of the integrated circuit and generates a control signal when the temperature exceeds a selected threshold temperature magnitude. The output of the each current sensor is independently combined with the control signal from the temperature sensor to disable the corresponding voltage regulator circuit when the temperature exceeds the threshold magnitude coincident with an excess current produced by the regulator.

Abstract: An apparatus for supplying current to a subscriber telephone set (R.sub.L) connected to a telephone exchange via a two-wire line departing from a a-wire and a b-wire output terminal in the arrangement. The arrangement includes two analogue amplifiers (2, 3) each with its output connected to said respective a-wire and b-wire output terminal, through which the combined DC-current and current representing the speech signal are fed out to the line. The apparatus further includes a voltage source with the pole voltage (E.sub.B) and its poles connected to two voltage supply inputs on each amplifier (2, 3), the output of the first amplifier (2, 3) being kept at a fixed potential. Three signal sources (5, 6, 8) are connected to the inputs of the amplifiers, the respective signal contribution of these sources being added for controlling the output magnitudes of the amplifiers. A first signal source (6) constitutes the reference signal source and has a fixed signal contribution.

Abstract: An apparatus for applying current to a subscriber line telephone set (RL) with associated two-wire line connected to a telephone exchange. The apparatus includes two analog amplifiers (5,6) each with its output connected to one of the two wires of the line, and feeding out on the line the combined DC current and current representing the speech signal. A DC/DC converter supplies voltage to an at least one of the amplifiers. To form a control voltage to the DC/DC converter, a cascade connection of a differential amplifier (1), a lowpass filter (2) and an adding circuit (3) are arranged between the line connection terminals and the control signal input of the DC/DC converter.

Abstract: An apparatus for generating a constant dc output voltage from a dc input voltage having a varying magnitude includes an inductor for storing an electrical charge and a semiconductor switch for controlling the application of the input voltage to the inductor. The apparatus further includes an error amplifier which compares the output voltage to a reference voltage and generates an error signal voltage proportional to the difference between the two voltages. An analog voltage divider generates a control voltage proportional to the ratio of the error signal voltage to the input voltage. The control voltage is applied to a pulse width converter which controls the duty cycle of the semiconductor switch responsive to changes in the input voltage such that the output voltage remains constant.

Abstract: A method in current feed to a subscriber telephone from a telephone exchange in which there is arranged a voltage source (11). A differential amplifier (1) senses the potential difference between the terminals of the voltage source (11), and after low pass filtering (2) a reference voltage (UREF) is added (3). The thus-obtained sum voltage is allowed to constitute the reference value in the system. The arithmetical mean value of the terminal potentials of the voltage source is utilized as a corresponding actual value. The difference between these reference and actual values is allowed to control a current tap in equal phase from both terminals of the voltage source.

Abstract: A lead frame for an electric microphone which includes an H-shaped structure of thin metallic material including spaced parallel legs and a crossbar therebetween. A first plate is spaced from the crossbar and is located between the legs. A lead connects the first plate to the crossbar. A second plate is spaced from the first plate and is connected thereto by a lead. All of the above structure is monolithic and coplanar being formed of a thin metallic material. The second plate is provided with holes and a amplifier chip is mounted on the first plate. Leads are provided connecting the chip with the aforesaid legs. The above structure is entrapped between two case halves and a metallized film is supported between the halves and in spaced parallel relationship with the second plate being supported on distant pieces. A cover encircles the case halves.

Abstract: An overvoltage guard for electronic circuits protects the connections from voltage transients which exceed the supply voltage of the circuit. The transients are bypassed to the grounded terminal of the supply voltage source by a thyristor connected between the terminal and the grounded terminal, the gate electrode of the thyristor being connected to the ungrounded terminal via a diode. Between the terminal and the grounded terminal there is conventionally connected a limiting diode.

Abstract: A gain control circuit includes at least a first (T1, T2) and a second (T3, T4) transistor differential amplifier the input circuits of which are connected in parallel to a signal voltage source. The gain control is performed by distributing a constant current (Is) between these differential amplifiers as a function of a control quantity (Uc) for setting the transconductance of the stages in a complementary way. The two differential amplifiers are provided with negative feed back (F, R1, R2, R3) but with different feed back factors. As the transistors in the differential amplifiers carrying signals of the same phase are interconnected the output signal from the automatic gain control circuit will consist of a superposition of the output signals of the two differential amplifiers.