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US 4,538,296 AGranted
Sound inhibitor for audio transducers
OwnerRobert S. Short, Mark S. Utterinventors
Life of this patent
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Abstract
A protection circuit for limiting the sound pressure level provided by transducer loads, such as headphones, in which there is provided interconnections between the input to the transducer load and the transducer load such that when loudness exceeds a predetermined limit, the connection to the transducer load is opened and the circuit turns off the audio signal to the transducer load and optionally illuminates an LED. After a predetermined time interval, the circuit automatically resets; however, if the sound pressure level has not been reduced below the predetermined limit, the circuit again immediately turns off the audio signal to the transducer load and this is continued until such time as the sound pressure level is reduced below the predetermined limit.
Claims21
A protection circuit for limiting the sound pressure level provided by a transducer load but otherwise not interfering with the flow of audio signal current to said transducer load comprising:
- (a) audio signal prevention means to immediately prevent audio signal current from reaching the transducer load which includes:
- (i) means to sense voltage applied to the transducer load, and
- (ii) means to increase said voltage, and
- (iii) means to use said increased voltage when it exceeds a predetermined level to immediately prevent the audio signal current from reaching the transducer load,
- (b) audio signal reestablishment means to reestablish the audio signal current to the transducer load after a fixed interval of time, and
- (c) audio signal reprevention means to again prevent the audio signal current from reaching the transducer load in the event that said increased voltage still exceeds said predetermined level, and
- (d) repeating means to repeat the functions described in subparagraphs (b) and (c) above sequentially until said increased voltage does not exceed said predetermined level at which time said audio signal is allowed to reach the transducer load.
4 more elements
A protection circuit for limiting the sound pressure level provided by a transducer load but otherwise not interfering with the flow of audio signal current to said transducer load comprising:
- (A) audio signal prevention means to immediately prevent audio signal current from reaching the transducer load which includes:
- (i) means to sense voltage applied to the transducer load, and
- (ii) means to use said voltage when it exceeds a predetermined level to immediately prevent the audio signal current from reaching the transducer load,
- (B) audio signal reestablishment means to reestablish the audio signal current to the transducer load after a fixed interval of time,
- (C) audio signal reprevention means to again prevent the audio signal current from reaching the transducer load in the event that said voltage still exceeds a predetermined level, and
- (D) repeating means to repeat the functions described in subparagraphs (B) and (C) above sequentially until said voltage does not exceed said predetermined level at which time said audio signal is allowed to reach the transducer load.
- which audio signal prevention means, audio signal reestablishment means, audio signal reprevention means and repeating means, in combination, include:
- (a) means for connecting two separate left and right audio signals from an amplifier output to a transducer load through normally open relay contacts,
- (b) means for controlling said relay contacts such that closing the contact on a power switch causes the relay contacts to close thereby allowing audio signal to pass through said relay contacts to said transducer load, and
- (c) means for connecting said audio signal to voltage isolating resistors,
- (d) means for coupling said audio signal to control the terminal of a voltage sensing semiconductor switch means so that exceeding a predetermined voltage level opens said relay contacts so as not to permit passage of audio signal to said transducer load,
- (e) timing means including an RC network in parallel with the anode and cathode of said semiconductor switch means to control the conducting state of the semiconductor thereby providing means to interrupt the audio signal through said relay contacts for a predetermined time as determined by said RC network, and
- (f) D.C. power supply across said timing means and in series with said power switch contact and said relay contacts such that closing of the normally open switch contact permits operation of the protection circuit and the timing means for controlling the length of the audio signal interruption.
10 more elements
A protection circuit for limiting the sound pressure level provided by a transducer load comprising:
- (A) audio signal prevention means to immediately prevent audio signal current from reaching the transducer load which includes:
- (i) means to sense voltage applied to the transducer load, and
- (ii) means to use said voltage when it exceeds a predetermined level to immediately prevent the audio signal current from reaching the transducer load,
- (B) audio signal reestablishment means to reestablish the audio signal current to the transducer load after a fixed interval of time,
- (C) audio signal reprevention means to again prevent the audio signal current from reaching the transducer load in the event that said voltage still exceeds a predetermined level, and
- (D) repeating means to repeat the functions described in subparagraphs (B) and (C) above sequentially until said voltage does not exceed said predetermined level at which time said audio signal is allowed to reach the transducer load,
- which audio signal prevention means includes:
- (a) means for connecting two separate left and right audio signals to the transducer load through two series resistors which have a relatively low resistance in relation to the transducer load,
- (b) means for connecting two isolated contacts of a relay directly in parallel with the respective said left and right audio signals so that exceeding a predetermined voltage level closes both contacts thereby shorting out said left and right audio signals to common and causing interruption of said audio signals to said transducer load,
- (c) means for connecting said audio signal to voltage isolating resistors,
- (d) means for coupling said audio signal to control the terminal of a voltage sensing semiconductor switch means so that exceeding a predetermined voltage level opens said relay contacts so as not to permit passage of audio signal to said transducer load,
- (e) timing means including an RC network in parallel with the anode and cathode of said semiconductor switch means to control the conducting state of the semiconductor thereby providing means to interrupt the audio signal through said relay contacts for a predetermined time as determined by said RC network, and
- (f) D.C. power supply across said timing means and in series with said power switch contact and said relay contacts such that closing of the normally open switch contact permits operation of the protection circuit and the timing means for controlling the length of the audio signal interruption.
10 more elements
Dependencies are inferred from the claim text.