Microphone output limiter
First Claim
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1. A microphone output limiter, comprising:
- a. a microphone having a pair of output terminals;
b. a pre-amplifier having a pair of input terminals operably connected to said pair of microphone output terminals;
c. a threshold level detector having a pair of input lines, each separately connected to said pre-amplifier input terminals, said threshold level detector having an output line;
d. a variable impedance device having an input circuit connected to said threshold level detector output line and a pair of output lines operably connected to said pre-amplifier input terminals; and
e. said variable impedance device producing a shunt load impedance at said pair of input terminals of said pre-amplifier in response to a control signal from said threshold level detector, which control signal is generated whenever said microphone generates a signal that exceeds a preselected level set within said threshold level detector.
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Abstract
A microphone output limiter which detects the amplitude of a microphone and produces a control signal which lowers the microphone'"'"'s impedance when the amplitude of the audio signal exceeds a preselected threshold level. The output signal is detected at the output of the microphone or it may be detected at the output of a later pre-amplifier stage. Once a control signal is generated it is coupled to a variable impedance device which produces a shunt load impedance across the output of the microphone thereby lowering its impedance. The microphone, as well as the variable impedance device, may be coupled through impedance converters in order to facilitate component matching.
30 Citations
23 Claims
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1. A microphone output limiter, comprising:
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a. a microphone having a pair of output terminals;
b. a pre-amplifier having a pair of input terminals operably connected to said pair of microphone output terminals;
c. a threshold level detector having a pair of input lines, each separately connected to said pre-amplifier input terminals, said threshold level detector having an output line;
d. a variable impedance device having an input circuit connected to said threshold level detector output line and a pair of output lines operably connected to said pre-amplifier input terminals; and
e. said variable impedance device producing a shunt load impedance at said pair of input terminals of said pre-amplifier in response to a control signal from said threshold level detector, which control signal is generated whenever said microphone generates a signal that exceeds a preselected level set within said threshold level detector. - View Dependent Claims (2, 3, 4)
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5. A microphone output limiter, comprising:
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a. a microphone having a pair of output terminals;
b. a pre-amplifier having a pair of input terminals operably connected to said pair of microphone output terminals and an output circuit;
c. a threshold level detector having an input line connected to said pre-amplifier output circuit, said threshold level detector having an output line;
d. a variable impedance device having an input circuit connected to said threshold level detector output line, and a pair of output lines;
e. an impedance converter having a first winding connected to said pair of output lines of said variable impedance device and a second winding connected to said pair of input terminals of said pre-amplifier; and
f. said variable impedance device producing a shunt load impedance at said pair of input terminals of said pre-amplifier through said impedance converter in response to a control signal from said threshold level detector, which control signal is generated whenever said pre-amplifier output circuit generates a signal that exceeds a preselected level set within said threshold level detector. - View Dependent Claims (6, 7, 8)
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9. A microphone output limiter, comprising:
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a. a microphone having a pair of output terminals;
b. an impedance converter, having a first winding connected to said pair of output terminals of said microphone, and a second winding;
c. a pre-amplifier having a pair of input terminals operably connected to said second winding of said impedance converter, and an output circuit;
d. a threshold level detector having an input line connected to said pre-amplifier output circuit, said threshold level detector having an output line;
e. a variable impedance device having an input circuit connected to said threshold level detector output line and a pair of output lines and operably connected to said pre-amplifier input terminals; and
f. said variable impedance device producing a shunt load impedance at said pair of input terminals of said pre-amplifier in response to a control signal from said threshold level detector, which control signal is generated whenever said pre-amplifier output circuit generates a signal that exceeds a preselected level set within said threshold level detector. - View Dependent Claims (10, 11, 12)
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13. A microphone output limiter, comprising:
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a. a microphone having a pair of output terminals;
b. an impedance converter having a first winding, a second winding connected to said pair of microphone output terminals, and a third winding;
c. a pre-amplifier having a pair of input terminals operably connected to said third winding of said impedance converter, and an output circuit;
d. a threshold level detector having an input line connected to said pre-amplifier output circuit, said threshold level detector having an output line;
e. a variable impedance device having an input circuit connected to said output line of said threshold level detector, and a pair of output lines connected to said first winding of said impedance converter; and
,f. said variable impedance device producing a shunt load impedance at said pair of input terminals of said pre-amplifier through said impedance converter in response to a control signal from said threshold level detector, which control signal is generated whenever said pre-amplifier output circuit generates a signal that exceeds a preselected level set within said threshold level detector. - View Dependent Claims (14, 15, 16)
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17. An output limiter for controlling a microphone signal level input to a pre-amplifier having an input circuit and an output circuit, said limiter comprising:
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a. a threshold level detector connected to said output circuit of said pre-amplifier for detecting an output signal therefrom to generate a control signal whenever said output signal exceeds a preselected level;
a variable impedance device operably connected to said threshold level detector for receiving said control signal to produce a shunt load impedance; and
c. an impedance converter having at least two windings operably connected between said microphone and said pre-amplifier and also connected to said variable impedance device for accommodating the requirement of the input impedance of said input circuit of said pre-amplifier. - View Dependent Claims (18, 19, 20, 21, 22)
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23. A microphone limiter, comprising:
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a. a microphone having an output impedance and a pair of output terminals;
b. an impedance transformer having at least one pair of input terminals coupled to said pair of output terminals of said microphone and a pair output terminals;
c. a pre-amplifier having an input coupled said pair of output terminals of said impedance transformer and an output;
c. a threshold level detector coupled to said output of said pre-amplifier for generating a control signal whenever said pre-amplifier output level exceeds a predetermined level;
d. a variable impedance device having a pair of impedance terminals coupled to said pair of output terminals of said microphone and a control input coupled to said control signal of said threshold level detector; and
e. said variable impedance device proportionally reduces the load impedance across said microphone output terminals, consequently attenuating and limiting said microphone output level, in response to said control signal of said threshold level detector whenever said pre-amplifier output level exceeds a predetermined level.
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Specification