FM Receiver for reception of special announcements and general programs
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 carrier frequency,said auxiliary carrier being amplitude-modulated by at least one frequency within a predetermined frequency band;
- a detector means connected to the radio frequency and tuning stage for detecting the auxiliary carrier signal of the predetermined auxiliary carrier frequency;
an amplitude demodulator connected to the detector and detecting the amplitude modulation of the auxiliary carrier;
a switchable output stage;
a switch connected to the amplitude demodulator adapted to be controlled by the amplitude modulation of the auxiliary carrier and connected to the switchable output stage;
a frequency selection filter tuned to pass at least one predetermined frequency of a frequency band of amplitude modulation on the auxiliary carrier, connected to receive the detected modulation from the amplitude demodulator, and providing an output signal representative of the level of amplitude modulation of the auxiliary carrier by said at least one predetermined frequency;
means for detecting amplitude modulation of the auxiliary carrier by at least said one predetermined frequency of the frequency band;
the improvement comprisingmeans for detecting change in the lever of percent of amplitude modulation of the auxiliary subcarrier by an least said predetermined frequency of said frequency band;
and level sensing means responsive to said level of percent of amplitude modulation detecting means for providing a switching control signal to said switch when the level of percent of modulation of said auxiliary carrier by at least said predetermined frequency of said frequency band changes by a significant value from a previously existing percent level of modulation.
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 is essentially continuously modulated by region or radio-station recognition signals, the level of which changes when the announcement recognition signal is radiated, the subcarrier is filtered in the receiver, demodulated, and the degree of modulation by the frequency characteristics of the region or radio-station recognition frequency (RR) is sensed. If the modulation of the subcarrier at this frequency or frequency band (RR) drops from, for example, 60% modulation to 30% modulation, or less--a 50% level change--a switch (4) is activated which inhibits transmission of audio programs from an external source, such as a tape recorder (5), a tuner tuned to another station, or the like, and reproduces the program or announcement being broadcast by the station to which a region or radio-station recognition frequency is assigned. Termination of the AR signal (FIG. 3: t2), forming the AR modulation on the 57 kHz subcarrier, causes the switch (4) to revert for reproduction of previously controlled audio information upon increase in the level of the RR modulation on the subcarrier, which is sensed in a modulation sensing circuit or network (FIG. 2: 34-37).
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Citations
34 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 carrier frequency, said auxiliary carrier being amplitude-modulated by at least one frequency within a predetermined frequency band; -
a detector means connected to the radio frequency and tuning stage for detecting the auxiliary carrier signal of the predetermined auxiliary carrier frequency; an amplitude demodulator connected to the detector and detecting the amplitude modulation of the auxiliary carrier; a switchable output stage; a switch connected to the amplitude demodulator adapted to be controlled by the amplitude modulation of the auxiliary carrier and connected to the switchable output stage; a frequency selection filter tuned to pass at least one predetermined frequency of a frequency band of amplitude modulation on the auxiliary carrier, connected to receive the detected modulation from the amplitude demodulator, and providing an output signal representative of the level of amplitude modulation of the auxiliary carrier by said at least one predetermined frequency; means for detecting amplitude modulation of the auxiliary carrier by at least said one predetermined frequency of the frequency band; the improvement comprising means for detecting change in the lever of percent of amplitude modulation of the auxiliary subcarrier by an least said predetermined frequency of said frequency band; and level sensing means responsive to said level of percent of amplitude modulation detecting means for providing a switching control signal to said switch when the level of percent of modulation of said auxiliary carrier by at least said predetermined frequency of said frequency band changes by a significant value from a previously existing percent level of modulation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. In a radio receiving system having a 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 in recognition of a control signal portion with respect to a received signal which contains 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 region or radio-station recognition frequency signal with a predetermined frequency within a recognition frequency band, the improvement comprising the steps of filtering the auxiliary subcarrier from the received signal; -
determining different levels of percent of amplitude modulation of said subcarrier at said predetermined frequency in said frequency band; and providing an output signal representative of a change of at least one level of percent of amplitude modulation of the subcarrier by said recognition signal for controlling the audio output stage. - View Dependent Claims (16, 17)
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18. 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 level of percent of amplitude modulation of the auxiliary carrier by the first recognition signal modulating the auxiliary carrier; and means connected to the detecting means for controlling the receiver reproduction to reproduce the special broadcast only when the level of percent of amplitude modulation detected by the detecting means falls below a predetermined percentage level of the auxiliary carrier. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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- 29. 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 amplitude modulation of an auxiliary subcarrier at a preselected frequency of a first recognition signal and for producing an output when the percent amplitude of modulation level of the first recognition signal is below 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 below the predetermined value is detected.
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32. A method of detecting and reproducing a special broadcast including monitoring radio broadcasts for an auxiliary carrier;
- determining whether said auxiliary carrier, when present 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 percent of amplitude modulation of the auxiliary carrier at the first frequency falls below a predetermined value, and switching the special broadcast to an audio output stage when the first frequency is below the predetermined value.
- View Dependent Claims (33, 34)
Specification