FM Receiver for general programs and special announcements
First Claim
1. FM receiver havinga radio frequency and tuning stage and a demodulator connected thereto for frequency demodulation of received signals including a carrier signal and an auxiliary carrier signal of a predetermined auxiliary subcarrier frequency, said auxiliary carrier being amplitude modulated by at least one modulation signal and, selectively, by at least one further modulation signal;
- a detector means connected to the radio frequency and tuning stage for detecting an auxiliary carrier signal for a predetermined auxiliary carrier frequency;
an amplitude demodulator connected to the detector and detecting amplitude modulation on the auxiliary carrier;
a switchable output stage;
a switch connected to the amplitude demodulator and adapted to be controlled as a function of the amplitude modulation of the auxiliary carrier and connected to the switchable output stage;
comprising,means for detecting amplitude modulation of the auxiliary carrier over the entire frequency range of amplitude modulation of the auxiliary carrier;
and level sensing means responsive to said modulation detecting means for providing a switching control signal to said switch when the level of modulation of all the modulation signals on the auxiliary carrier differs by a significant value from a predetermined and detectable modulation level.
1 Assignment
0 Petitions
Accused Products
Abstract
To improve reliability of recognition of an announcement recognition (AR) signal radiated by a transmitter upon broadcasting an announcement (e.g. traffic information, news, etc.), in the form of AM modulation of a 57 kHz auxiliary subcarrier, in which the subcarrier may also be modulated by other control signals, the subcarrier is filtered in the receiver, demodulated, and the degree of all modulations, regardless of frequency, on the subcarrier is sensed, and if the modulation changes significantly, for example rises from 60% modulation to 90% modulation (50% change), a switch (4) is activated which inhibits transmission of audio programs from an external source, such as a tape recorder (5), tuner tuned to another station, or the like, and reproduces the announcement being broadcast; termination of the AR signal, forming the AR modulation on the subcarrier, causes the switch to revert for reproduction of previously controlled audio information.
35 Citations
31 Claims
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1. FM receiver having
a radio frequency and tuning stage and a demodulator connected thereto for frequency demodulation of received signals including a carrier signal and an auxiliary carrier signal of a predetermined auxiliary subcarrier frequency, said auxiliary carrier being amplitude modulated by at least one modulation signal and, selectively, by at least one further modulation signal; -
a detector means connected to the radio frequency and tuning stage for detecting an auxiliary carrier signal for a predetermined auxiliary carrier frequency; an amplitude demodulator connected to the detector and detecting amplitude modulation on the auxiliary carrier; a switchable output stage; a switch connected to the amplitude demodulator and adapted to be controlled as a function of the amplitude modulation of the auxiliary carrier and connected to the switchable output stage; comprising, means for detecting amplitude modulation of the auxiliary carrier over the entire frequency range of amplitude modulation of the auxiliary carrier; and level sensing means responsive to said modulation detecting means for providing a switching control signal to said switch when the level of modulation of all the modulation signals on the auxiliary carrier differs by a significant value from a predetermined and detectable modulation level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. In a radio receiving system having an FM radio receiver, an audio output stage including switching means switchable among various audio signal sources in addition to the FM receiver a method of removing ambiguities of recognition of a control signal with respect to a received signal which includes a control signal portion and other signal portions,
in which the received signal is a frequency-modulated (FM) signal and includes an auxiliary subcarrier within its frequency band, said subcarrier being amplitude-modulated by at least one recognition frequency signal and, selectively, by a further recognition frequency signal within a recognition frequency band, the signal having said recognition frequencies forming the control signal portion, the improvement comprising the steps of filtering the auxiliary subcarrier from the received signal; -
detecting total modulation level of amplitude modulation of the subcarrier by the two recognition signals and providing an output signal representative of the total level of amplitude modulation of the subcarrier for controlling the audio output stage. - View Dependent Claims (14, 15)
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16. A radio receiver including,
means responsive to radio broadcasts of assigned frequency for reproducing regular program content; -
means responsive to an auxiliary carrier of predetermined frequency amplitude modulated with first and second recognition signals at first and second recognition signal frequencies for causing said receiver to reproduce an auxiliary special broadcast; the means responsive to the auxiliary carrier including means for detecting the combined level of modulated amplitude of the auxiliary carrier by the first and second recognition signals modulating the auxiliary carrier; and means connected to the means for detecting for controlling the receiver reproduction to reproduce the special broadcast only when the combined level of modulation amplitude detected by the detecting means exceeds a predetermined percentage level of the auxiliary carrier. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25)
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- 26. For use in an FM radio receiver having a tuner, an RF stage, an output audio stage including switching means switchable among various audio signal sources in addition to the FM receiver, the improvement comprising means for detecting total amplitude modulation of an auxiliary subcarrier of a preselected frequency value by at least two distinct recognition signals at two distinct frequencies and for producing an output when the modulation by the two recognition signals exceeds a predetermined value, and means responsive to the output from said means for detecting for controlling said switching means to connect the receiver to its audio stage when said modulation above a predetermined value is detected.
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29. A method of detecting and reproducing a special broadcast including monitoring radio broadcasts for an auxiliary carrier;
- determining whether said auxiliary carrier, when presents contains at least one of a first and second recognition signal amplitude modulating the auxiliary carrier at at least one of a first and second frequency, determining whether the total of the amplitude modulation of the auxiliary carrier at the first and second frequencies exceeds a predetermined value, and switching the special broadcast to an audio output stage when the total of the amplitude modulation at the first and second frequencies exceeds the predetermined value.
- View Dependent Claims (30, 31)
Specification