Emergency broadcast alert detector

• US 4,633,515 A
• Filed: 04/09/1984
• Issued: 12/30/1986
• Est. Priority Date: 04/09/1984
• Status: Expired due to Fees

• Current Assignee: Crown Industries, Inc.
• Original Assignee: Harry B. Uber
• Inventors: Uber, Harry B., Staschek, George Jr.
• Primary Examiner(s): Ng, Jin F.
• Assistant Examiner(s): Huseman, M.
• Application Number:
  US06/598,210
• Time in Patent Office: 995 Days
• Field of Search: 455/32, 455/35, 455/33, 455/57, 455/161, 455/169, 455/166, 455/195, 455/227, 455/228, 455/229, 455/156, 381/24, 381/25, 381/74, 381/120, 381/123, 340/648, 340/329, 331/179
• US Class Current: 455/161.3
• CPC Class Codes: H03J 7/28 using counters or frequency dividers

Abstract

An emergency broadcast alert detector having a radio receiver scanning among several predetermined frequencies. The audio output of the radio receiver is connected to a noise detector that allows scanning to continue as long as noise indicative of no signal being received is present on the audio output. When the radio receiver scans to a frequency on which a broadcast is present, the lack of noise on the audio output of the receiver causes scanning to discontinue. The audio output is also connected to a tone detector that generates an alarm for a predetermined period in the even that an alert tone of a predetermined frequency is present on the audio output of the radio receiver.

Claims

1. In an emergency warning system in which an "alert" tone, indicative of an emergency condition, is transmitted by at least one of several stations on respective transmission frequencies, an emergency broadcast alert detector comprising:

(a) a radio receiver having an audio signal output and a tuner scanning among said transmission frequencies, sand tuner having;

a local oscillator including a crystal substantially controlling the frequency of said local oscillator signal, said local oscillator signal further including a plurality of reactive elements connected to said crystal and a plurality of diodes connected with some of said reactive elements in a manner that switches the reactance of the respective reactive elements between two states, depending upon whether or not current is flowing through said diodes, said diodes being connected to respective frequency selection inputs of said local oscillator so that the frequency of said local oscillator signal is pulled from the resonant frequency of said crystal by said reactive elements being switched by current flowing from said frequency selection inputs through said diodes;

a mixer receiving the output of said local oscillator and a transmitted signal, said mixer selecting a transmitted signal having a frequency equal to the sum of or difference between a fixed intermediate frequency and said local oscillator frequency;

a decoder connected to the output of said mixer, said decoder generating as said audio output a signal corresponding to the modulation on the transmitted signal selected by said local oscillator;

a clock generator producing a clock signal adapted to cause said tuner to scan from one transmission frequency to the next;

a sequencer having a clock input and outputs connected to the frequency selection inputs of said local oscillator, said sequencer sequentially applying combinations of logic levels to said local oscillator responsive to clock pulses applied to said clock input; and

a gate having its output connected to the clock input of said sequencer and inputs receiving said clock signal from said clock generator and a disable signal to gate said clock signal to the clock input of said sequencer when said disable signal is not being generated;

(b) a noise detector connected to the audio output of said radio receiver, said detector generating said disable signal except when said noise detector detects noise at said audio output, thereby indicating that no signal is being transmitted on the transmission frequency selected by said tuner, whereby said tuner continues to scan among said transmission frequencies until said tuner tunes to a station that is transmitting a signal;

(c) a tone detector connected to the audio output of said radio receiver, said tone detector generating an alarm signal when said "alert" tone is present at said audio output; and

(d) an alarm connected to said tone detector, said alarm generating a visual or audible alarm responsive to receipt of said alarm signal.

2. In an emergency warning system in which an "alert" tone, indicative of an emergency condition, is transmitted by at least one of several stations on respective transmission frequencies, an emergency broadcast alert detector comprising:

a radio receiver having an audio signal output and a tuner scanning among said transmission frequencies, said tuner having a disable input that prevents said scanning from continuing responsive to a disable signal;

a noise detector connected to the audio output of said radio receiver, said detector generating said disable signal except when said noise detector detects noise at said audio output, thereby indicating that no signal is being transmitted on the transmission frequency selected by said tuner, whereby said tuner continues to scan among said transmission frequencies until said tuner tunes to a station that is transmitting a signal;

a tone detector connected to the audio output of said radio receiver, said tone detector generating an alarm signal when said "alert" tone is present at said audio output; and

an alarm connected to said tone detector, said alarm comprising;

a timer connected to the output of said tone detector, said timer generating an output signal for a predetermined period after the start of the alarm signal from said tone detector;

an oscillator generating a switching signal;

a signaling device generating a visual or audible alarm responsive to receipt of a signal at an enable input; and

a gate having an output connected to the enable input of said signaling device and inputs receiving said output signal from said timer and said switching signal from said oscillator, said gate applying said switching signal to the enable input of said signaling device upon receipt of said output signal from said timer, thereby intermittently enabling said signaling device for said predetermined period.

3. An emergency broadcast alert detector for generating an alarm upon the occurrence of an "alert" tone on at least one of several radio frequencies, comprising:

a radio receiver having an audio output;

scanning means for causing said radio receiver to sequentially receive each of said radio frequencies as determined by the frequency of a local oscillator signal, comprising;

a local oscillator generating said local oscillator signal, said local oscillator signal having a frequency that determines the radio frequency to which said radio receiver is tuned, said local oscillator generating a local oscillator signal of a predetermined local oscillator frequency that is a function of the logic levels applied to the said frequency selection inputs;

a clock generator producing a clock signal adapted to cause said local oscillator to sequentially switch among several local oscillator frequencies;

a sequencer having a clock input and outputs connected to the frequency selection inputs of said local oscillator, said sequencer sequentially applying combinations of logic levels to said local oscillator responsive to clock pulses applied to said clock input; and

a gate having its output connected to the clock input of said sequencer and inputs receiving said clock signal from said clock generator and a disable signal to gate said clock signal to the clock input of said sequencer when said disable signal is not being generated;

means for generating said disable signal in the event that a signal is received by said radio receiver on one of said radio frequencies, thereby preventing said sequencer from causing said radio receiver to switch from one radio frequency to the next;

tone detector means connected to the audio output of said radio receiver for generating an alarm signal upon detecting said "alert" tone in the signal received by said radio receiver; and

alarm means connected to said tone detector means for generating an audible or visual alarm upon receipt of said alarm signal.

4. The emergency broadcast alert detector of claim 3 wherein said local oscillator includes a crystal substantially controlling the frequency of said local oscillator signal, said local oscillator further including a plurality of reactive elements connected to said crystal and a plurality of diodes connected with some of said reactive elements in a manner that switches the reactance of the respective reactive element between two states, depending upon whether or not current is flowing through said diodes, said diodes being connected to the frequency selection inputs of said local oscillator so that the frequency of said local oscillator signal is pulled from the resonant frequency of said crystal by said reactive elements being switched by current flowing from said frequency selection inputs through said diodes.