Abstract: A telephone branch line transmission circuit includes a control device which receives dial pulses and in response thereto controls at least two switching devices arranged between two branch lines to a telephone exchange. A blocking capacitor is coupled to the first switching device. In order to prevent charging of such capacitor from distorting the current supplied from the exchange at the end of a dial pulse, the first switching device is included between the blocking capacitor and one of the branch lines. The connection node thereof with the blocking capacitor is connected to a terminal of a second switching device, another terminal of which is coupled to the second branch line. The control terminal of the second switching device is connected to a storage capacitor. In the off-state of the switching devices no residual direct current can flow from the exchange to charge the blocking capacitor.

Abstract: A subscriber line control circuit for controlling a reversing switch to couple a subscriber station either to an AC signalling voltage generator or to a DC line voltage supply, depending on whether the subscriber station is on-hook or off-hook. The control circuit includes a capacitor connected between the subscriber line and the reversing switch and which by means of a rectifier is charged to a DC charge voltage by alternate half cycles of the AC signalling voltage. During the other half cycles the DC charge voltage superimposes on the AC signalling voltage and so is available for actuating an automatic switching arrangement by which the subscriber station is selected for coupling to the reversing switch. When the subscriber station goes off-hook the capacitor discharges over the subscriber line, resulting in a change in voltage or current which is detected by a detection circuit.

Abstract: A circuit arrangement of simple structure for producing dialing pulses for a telephone transmission system so as to provide a relatively low insertion attenuation during transmission. The impedance of the transmission system should not be reduced. At loop closure the a.c. impedance of the circuit is high-ohmic and for d.c. current the circuit has a very low resistance. A switching apparatus is connected to the wires of a connecting line in parallel with the transmission system. The switching apparatus is arranged as a series connection of a bipolar transistor and a switching element consisting of a MOS field-effect transistor.

Abstract: The invention relates to a circuit for deriving output of signals and output counter cycle signals from a one-sided input signal.The circuit contains two transistors coupled to at least one current reflecting circuit. The two outputs of the current reflecting circuit are connected either with the emitters or the collectors of two transistors, whereby one connecting line at least one resistor is disposed. The interconnected bases of each of the two transistors are connected to an adjustable direct-current source. The equal electrodes of the two transistors which are not connected with the current reflection circuit form the signal output and the signal counter cycle output.

Abstract: A variable resistance device utilizes a control signal variable resistor and a first fixed resistor connected in series as a voltage divider as well as a second fixed resistor and an operational amplifier having an input connected between the first fixed resistor and one side of the variable resistor and an output connected through the second fixed resistor to the other side of the variable resistor, as a substantially linear variable resistance device where the variable resistance is obtained across the voltage divider.