US 3829856 A
A telephone visual paging system that is actuated by an audio signal. The audio input current is used to power two or more light emitting diodes which are housed on a telephone receiver. Other than the audio signal power supply, no separate power supply system is needed to power these light sources. By superimposing variations caused by the audio input signal on the periodic switching signals from a multivibrator, the light emitting diodes can generate a semaphore radiation action to get the visual attention of an observer. This invention is particularly useful in hazardous gaseous environments, like coal mines, where electric wiring connections and the possibility of ignitions from electric sources should be minimized.
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Description (OCR text may contain errors)
United States Patent Conroy et al.
[451 Aug. 13, 1974 PAGING VISUAL SIGNAL  Assignee: The United States of America as represented by the Secretary of the Interior, Washington, DC.
 Filed: Oct. 11, 1973  Appl. No.: 405,603
 US. Cl 340/366 R, 340/311, 340/148  Int. Cl. G08b 5/38  Field of Search.... 340/311, 148, 366 R, 366 B; 179/84 L  References Cited UNITED STATES PATENTS 3,586,919 6/1971 Harris 340/148 X Primary ExaminerHar0ld I. Pitts Attorney, Agent, or FirmThomas Zack; Frank A. Lukasik 57 ABSTRACT A telephone visual paging system that is actuated by an audio signal. The audio input current is used to power two or more light emitting diodes which are housed on a telephone receiver. Other than the audio signal power supply, no separate power supply system is needed to power these light sources. By superimposing variations caused by the audio input signal on the periodic switching signals from a multivibrator, the light emitting diodes can generate a semaphore radiation action to get the visual attention of an observer. This invention is particularly useful in hazardous gaseous environments, like coal mines, where electric wiring connections and the possibility of ignitions from electric sources should be minimized.
5 Claims, 2 Drawing Figures PAGING VISUAL SIGNAL I BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a visual paging system which is actuated by an inputted audio signal from a remote speaker. It does this without using any separate power source for the paging system. The paging system visually transmits a semaphoric rhythm from the observable light sources.
2. Description of the Prior Art In noisy environments where bells or other sound devices cannot be used, voice actuated lights have been used to alert observers that someone is trying to communicate with them on a telephone. Usually the intensity or frequency of the light source is varied as the speaker talks. An example of such a prior art reference is the U.S. Pat. No. 3,582,671 to James H. Ott. In all of the known prior art references, the power to actuate the light source is supplied from a power supply in the receiver in addition to the power source used to send the audio signal. To avoid the use of this separate power source for the paging light, we have invented a system that uses two or more light emitting diodes whose transmitted radiation variation is dependent on the combination of the signal from an audio amplifier and the switch-action of a multivibrator. I
By reducing the power sources needed to visually signal an observer in a noisy environment, which also has potentially hazardous gases, the number of points of possible ignition are also reduced. Thus, our invention is not only less costly to build, since it uses less parts, but it is also safer in many environments.
SUMMARY BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a telephone receiver in a mine with our visual paging system attached. FIG. 2 is a circuit diagram of the paging system.
DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates the preferred embodiment of the system housed in a generally closed telephone receiver housing 1. For descriptive purposes, this illustrated system will be referred to as the receiver system. An identical remote second system (not shown), into which the person who is initiating the paging speaks, is connected by wires to illustrated housing 1. This remote second system will be referred to as the speaker system. Two light emitting diodes 2 and 3 (LED) may be placed in a sideby-side relationship on one side of the receiver housing or if both housing sides are visually observable, a second set of LEDs 6 and 7 may be added. When the pager initially speaks the name of the person into the speaker system telephone, he simultaneously depresses a paging button, like button 13, on the speaker telephone. This action causes the dc voltage to be sent via telephone wires 9 to anamplifier unit located in the receiver system. A loudspeaker unit, located in receiver housing 1, is actuated by this amplifier and broadcasts the name spoken. At the same time this same signal is used to actuate the visual paging circuit shown in FIG. 2. The telephone handset is then picked up by the individual answering the page and he may speak into the microphone end 5 and listen into end 4. The receiver system of FIG. 1 can be held by a screw held bracket 10 to a mining wall 11.
FIG. 2 illustrates the visual paging circuit components of the system all of which, except for the handset, are in receiver housing I. Wires'9 are connected to the input of the rectifier bridge formed by interconnected diodes D D D and D These same wires carry the audio signal from the high impedance side of the speaker system paging amplifier transformer (not shown) which is connected in parallel with the loudspeaker voice coil. An optional transformer may also be used to step up the impedance to the level required for proper operation if the output voltage to the loudspeaker is not sufficiently high.
The rectified bridge functions to convert the incoming dc audio signal to a pulsating dc signal. Capacitor C, smooths this converted signal out somewhat. The two LEDs which were designated by numbers 2 and 3 of FIG. 1 are designated, respectively, as LED 2 and LED 3 in FIG. 2. Each LEDhas its associated biased based transistors T and T which receive the pulsating signal from the bridge if their associated transistor permits current flow. As is apparent from FIG. 2, the base of transistors T and T are energized by the remaining circuitry which is depicted within the dotted lines of FIG. 2.
The circuitry within the dotted lines having resistors R R R R R R and R capacitors C and C and transistors T and T functions as an astable multivibrator. Like the rest of the FIG. 2 circuit, it is powered by the rectified and smoothed input audio signal. When in an operative state, a signal from the loudspeaker induced by a speaker actuates the circuitry to send regular pulsating signals to LED 2 and LED 3 which are superimposed upon the variable frequency output from the multivibrator. The result is a visually appealing semaphore action between the LEDs that catches the eye of an observer and which is intrinsically safe and. yet consumes a lower power drain. The action is such that it alternately illuminates from-LED 2 to LED 3 and back in a regular manner with variations in frequency of alternation depending on the intensity of audio signal input. This intensity is directly related to the intensity of the voice of the speaker. When nobody is speaking into the distant microphone, there is no illumination of either of the LEDs.
Various types and values may be given to each of the circuit elements. For example, in the preferred working embodiment, the following values were used: Resistor R, 300 ohms, resistor R 3.3K ohms, resistors R R and R 22K ohms, resistors R and R 2.2K ohms, capacitors C, and C 35 p. farads, capacitor C 30 p. farads, transistors T and T 2N1893 type manufactured by Motorola Corp., transistors T and T 2N2540 type manufactured by Motorola or Texas Instruments, LED 2 and LED 3 aretypes MVIOB manufactured by Monsanto and bridge rectifiers are D D D and D type lDB2A manufactured by Intemational Rectifier Corporation. Other variations of manufacturers, types, and values are, of course possible as long as the total system functions in a complementary manner as intended.
The two additional LEDs designated by numbers 6 and 7 in FIG. 1 are not essential to theinvention, but are used only to show miners on the right hand side of the receiver (viewed in FIG. '1) a person is calling. They could be incorporated into the FIG. 2 circuitry by adding two parallel'legs each with one LED and one transistor connected in series, like LED 2 and transistor T between the points A'and B of FIG. 2. The base of each of these two added transistors would join the multivibrator circuit between transistor T and resistor R and, for the other added leg, between transistor T and resistor R It should be apparent that our invention accomplishes its intended stated objective. The circuitry described in FIG. 2 has no self-contained power source but acts rather as a passive unit until activated by an incoming audio signal. Thereafter, the LEDs pulsate at a frequency which is changed by the inputted audio signal to visually give the attention attracting semaphore effect. A delay in shut off is included to prevent the stopping of signalling between normal word interruptions or normal pauses in conversation. This delay is accomplished by capacitor C which has initially stored sufficient energy. During short voice pauses, it discharges this stored energy until it is depleted, at which time, the visual paging signal ceases. Variations, of course, are possible. While not preferred, the multivibrato r circuitry could be eliminated so that a variable frequency is emitted by LED which is dependent only on the audio input signal. However, the desired semaphore effect would be missing in such a modification.
Additional circuitry (not shown) allow the audio signal transmitted on wires 9 to be converted to sound when an observer picks up earpiece 4. The semaphore optical radiation usually stops shortly thereafter when this happens, depending on the arrangementof the additional circuitry with the system illustrated.
None of the specifically disclosed circuit elements or their arrangement or any disclosed features should be used to limit the scope and extent of this invention which is to be measured only by the scope of the claims which follow.
1. A visual paging system for attracting the attention of observers comprising:
means for inputting an amplified audio signal into the system;
circuitry to change the inputted audio signal to pulsating direct current signals;
a plurality of light emitting diodes operatively connected to said pulsating circuit; and
a switching circuit connected to said light emitting diodes such that in an operative state, it continuously switches the signals received by the light emitting diodes from'the pulsating circuit when there is an audio input signal.
2. The system of claim 1 wherein at least two of said light emitting diodes are connected by parallel circuits to each other.
3. The system of claim 1 wherein said pulsating circuitry comprises a rectifier bridge circuit in parallel with a capacitor.
4. The system of claim 1 wherein said switching circuit comprises an astable multivibrator connected by solid state devices to each of said light emitting diodes.
5. The system of claim 1 wherein said system is contained in a single housing and said light emitting diodes consist of four diodes, two on opposite sides of said housing.