U.S. Philips Corporation

Gilbert Petitjean

Michel Lebourg

Christian Le Tortorec

A variable attenuation device intended to be inserted between a transmitter circuit having a certain internal impedance and a load circuit; it composed of at least on parallel attenuation branch made up from a variable resistance component (in particular a p-i-n diode) and a bias circuit to vary the resistance of the component as a function of an attenuation control variable. The parallel attenuation branch has a limiting component which is connected in series with the variable resistance component and whose value ensures the matching of the internal impedance of the transmitter circuit.

Variable attenuation device intended to be inserted between a

A device for marking, for example, the position of a control knob, comprising an arrangement with several terminals each of which corresponds to one of the positions, the application of a DC voltage (+V) at each instant to one and only one of the terminals indicating the presence of the knob in the corresponding position. The device includes a series of operational amplifiers having specified gain, each amplifier having its inverting input connected to one of the terminals and its non-inverting input connected to the terminal corresponding to the next position. Each terminal is connected to a circuit for taking those terminals, which do not correspond to the momentary position of the knob, to a specified voltage. The outputs of the amplifiers are connected to a detection circuit for detecting on one of them any transition whose amplitude exceeds a specified threshold and to control a count-up/count-down device whose output value is incremented or decremented depending on the direction of the transition, this output value constituting an indication of the position of the knob.

Encoding device for multiple consecutive position detection

A PIN diode is in series in a high-frequency signal path between an input and an output, and is controllably biased either on or off by a control signal supplied thereto from the output of a control circuit in response to a command voltage. The control circuit derives the control signal from a positive voltage source when the diode is to be turned on and from a negative voltage source when the diode is to be turned off. The negative voltage must be a relatively high value, which can cause excessive power dissipation in the control circuit due to charging of the bypass capacitance present at the output terminal thereof for shunting high frequencies. To prevent that, the control circuit includes an overvoltage circuit which produces a short duration trigger pulse in response to change-over from the positive voltage source to the negative voltage source and which supplies a current pulse of brief duration for charging the bypass capacitance.

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Igny, France

Gilbert Petitjean