Title:
ATTENUATION CIRCUIT
Document Type and Number:
Japanese Patent JPS61239714
Kind Code:
A
Abstract:
An automatic linear compression circuit for a telephone «handsfree» loudspeaker is provided. The circuit consists of a variable attenuator the level of attenuation of which is controlled by the input signal level. The input signal is passed through a positive peak detector to obtain a time averaged signal corresponding to the average positive peak values of the input signal and this time average signal is compared against a time increasing reference voltage. As long as the reference voltage is below the value of the time averaged signal a positive attenuator control signal is derived. This positive control signal keeps the attenuator portion of the circuit operative. In the attenuator the input voltage is sampled to a first capacitor. The first capacitor is subsequently connected to and disconnected from a second capacitor a number of times as long as the positive attenuator control signal is present. Each time this is done the voltage on the first capacitor is reduced by a factor depending on the capacitances of the two capacitors. After a predetermined time the voltage remaining on the first capacitor is passed through buffers and another capacitor to provide an attenuated output. The circuit is simple and flexible, permitting wide ranges in the operating parameters to be achieved simply by including one or more variable capacitors.
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Inventors:
DEBITSUDO ROORENSU RINCHI
Application Number:
JP2986886A
Publication Date:
October 25, 1986
Filing Date:
February 13, 1986
Export Citation:
Assignee:
NORTHERN TELECOM LTD
International Classes:
H03G1/00; H03H19/00; H03G7/00; H03H17/00; H04M1/60; (IPC1-7): H03H19/00
Attorney, Agent or Firm:
Hideto Asamura
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