US3859629A - Speed alarm system for an automobile - Google Patents

Abstract

A speed alarm system for an automobile comprises a speed detector connected to the output of a generator for generating an output proportional in magnitude to a travelling speed of an automobile; a speed detector for detecting the travelling speed set to a predetermined level; an alarm signal generator operative to receive an output of the speed detector to generate two alarm signals displaced in phase from each other; and a sound reproducing device for generating from two speakers alarm sounds obtained by amplifying the outputs of the alarm signal generators.

Description

Unite States Patent Komiyama et a1. Jan. 7, 1975 [54] SPEED ALARM SYSTEM FOR AN 3,771,122 11/1973 Sattler 340/62 AUTOMOBILE [75] Inventors: Kazuo Komiyama, Tokyo; Takeharu Primary ExaminerAlvin H. Waring Niioka, Yokohama, both of Japan Attorney, Agent, or Firmblon, Fisher, Spivak, [73] Assignee: Tokyo Shibaura Electric Co., Ltd., Mcclenand & Ma'er Kawasaki-shi, Japan [22] Filed: May 9, 1973 57 ABSTRACT [21] Appl 358490 A speed alarm system for an automobile comprises a speed detector connected to the output of a generator [30] Foreign Application Priority Data for generating an output proportional in magnitude to May 15, 1972 Japan 47-47230 a travelling Speed of an automobile; a Speed detector for detecting the travelling speed set to a predeter- [52] US. Cl. 340/62, 340/263 mined level; an alarm Signal generator operative to [51] Int. Cl B60q 1/54 Ceive an Output of the Speed detector to generate two [58] e d of Search 340/53, 62, 253; alarm signals displaced in phase from each other; and 180/105 R [65' [2 10 a sound reproducing device for generating from two speakers alarm sounds obtained by amplifying the out- 5 R f r Cited puts of the alarm signal generators.

UNITED STATES PATENTS 8 Claims, 14 Drawing Figures 3,764,975 /1973 Hayden et a1 340/62 241. SPEED SETT (3 DEVICE DE 'l lgPOR g 1.1.1 U 22 Z I) bivifi aaaa GENERATOR PATENTED 71975 3.859.629 SHEEI 10F 7 Jqm m rm v "655% 85a Swim @zEwm Swim f ON mm PATENTED JAN 7 i975 SHEET 3 BF 7 FIG. 5

} ALARM SOUND PERFORMANCE SOUND v SETTING LEVEL VARIABLE ANGLE 9 OF THE SCUND VOLUME ADJUSTING RESISTOR F l G. 6

'FIG. 7

PATENTEB JAN 71975 sum 7 or 7 FIG.

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SPEED ALARM SYSTEM FOR AN AUTOMOBILE BACKGROUND OF THE INVENTION This invention relates to a speed alarm system of an automobile.

Recently, traffic accidents are increased in number with a wide acceptance of automobile and, particularly, excess speed results in an increased number of accidents.

A variety of devices are designed to give a warning to the drive when excess speed is attained.- The speed alarm devices are designed to light a lamp and sound a buzzer when a present speed is encountered. A lamp alarm is liable to be overlooked by the driver focussing his attention to the foreground. An alarm buzzer is difficult to draw the drivers attention due to its monotonous tone.

An object of this invention is to provide a speed alarm system for an automobile, capable of giving forth alarm sounds which easily attract the drivers attention.

SUMMARY OF THE INVENTION A speed detector is incorporated into an automobile and connected to the output of a generator for generating an output proportional in magnitude to the output of a travelling speed of an automobile. A speed setting device is coupled to the speed detector, is capable of being set to a predetermined speed and is operated when an output level corresponding to the setting speed is received from the speed detector. An alarm sound signal wave generator is operated by the operation of the speed setting device and generated desired alarm sound signal waves from two output terminals of the signal wave generator. The alarm sound signal wave generator is connected to a dual channel sound generating signal and generates alarm sounds from two speakers connected to the sound reproducing device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an automobile speed alarm system according to this invention;

FIGS. 2A and 2B are schematic circuits of FIG. 1;

FIG. 3 is a graphical representation showing a relation between the output voltage of a generator and the speedof an automobile;

FIG. 4 is a waveform of each part of a circuit of FIG.

FIG. 5 is a graphical representation showing a relation in sound volume between alarm sounds and car stereo performance sounds;

FIG. 6 is a perspective view showing the interior of an automobile equipped with a speed alarm system;

FIG. 7 shows a connection between the speed alarm system, a generator and a car stero set;

FIG. 8 is a perspective view showing the speed alarm device;

FIG. 9 is a side cross-sectional view showing the speed alarm device;

FIG. 10 is a perspective view showing a speed setting switch section;

FIG. 11 is a perspective view showing a mounting bracket of the speed alarm system; and

FIGS. 12 and 13 are a front view and a side view, respectively, of the speed alarm system incorporated into the speed alarm system.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1 there is shown aspeed setting device 20 adapted to be set selectively to a control speed as stipulated in a Road Traffic Law. When the travelling speed of an automobile reaches the setting speed, that is, the travelling speed exceeds the setting speed set at thespeed setting device 20, aspeed detector 21 is operated. The speed detector is coupled to analarm signal generator 22. An output signal of the detector as generated upon coincidence of the setting speed with the travelling speed is fed to analarm signal generator 22 to cause it to be operated. Thealarm signal generator 22 has two output terminals and adapted to generator alarm signals shifted in phase from each other. The output terminals of the alarm signal generator are connected, respectively, to the input terminals corresponding to the left and right channels of the dual channelsound reproducing device 23.

The sound reproducing device is a dual channel sound reproducing device, for example a car stereo set such as a stereo tape player or a car stereo cartridge tape recorder and an FM car stereo receiver. At the normal time, a stereophonic performance or broadcasting is effected and, at the warning time, alarm signals from thealarm signal generator 22 are amplified and generated from a speaker. At this time, a stereophonic performance sound is also generated from the speaker. The sound reproducing device is also so designed that an electric power is supplied from another line when aspeed detecting device 21 is operated. Even when the car stereo set is not used, alarm sounds can be generated due to a constant supply of electric current from said another line.

Let us now explain the detailed circuit of the alarm sound system of FIG. 2.

Agenerator 25 incorporated into an automobile generates an AC output voltage nearly proportional to the travelling speed of the automobile, as shown in FIG. 3. One end of the generator is grounded and the other end of the generator is connectedto aspeedlevel setting adjuster 26. The level setting adjuster consists of resistors Rl-R6 and a multicontact change-overswitch 27. Each of the resistors Rl -R6 has one end connected to the output of thegenerator 25 and the other end connected to any one of the contacts of the change-overswitch 27. A neutral contact of the changeover switch is grounded through a resistor R7 and connected to arectifier circuit 28 consisting of a diode D1 and a smoothing capacitor C1. Thelevel setting adjuster 26 is constituted of resistors whose resistances are accurately determined to correspond to respective travelling speeds based on the Road Traffic Law and, there fore, a more accurate speed setting is obtained than it is constituted of a potentiometer or continually variable resistor.

The output of the rectifyingcircuit 28 is connected through a biasing resistor R9 to a Schmittcircuit 29 including a first and a second transistor Trl and Tr2 and 5 grounded through a resistor R8. The output of the Schmitt circuit, that is, the collector of the transistor Tr2, is connected through a resistor R33 to the base of a third transistor Tr The collector of the third transistor is coupled to the base of each of parallel-connected amplification transistors Tr4, TrS and Tr6 in a. drivecircuit 30.

The alarmsignal generating circuit 22 is connected through a resistor 10 to the output of thedrive circuit 30 and consists ofa modulationwave oscillating circuit 31, a first and a second modulation waveform shaping circuit 32 and 33, a soundsignal oscillation circuit 34 and anoutput circuit 35 consisting of adifferential circuits 351 and 352 and afilter 353. The modulation wavesignal oscillating circuit 31 includes two transistors Tr7 and Tr8 and constitutes a conventional astable multivibrator having two output ends. The first modulation waveform shaping circuit 32 consists ofa capacitor C3a connected to one output of theastable multivibrator 31, a breeder or voltage dividing circuit consisting of resistors Rl3a and R14a, a transistor circuit including a resistor RlSa and a transistor Tr9 connected to the breeder circuit, and a wave form shaping capacitor C4a connected between the emitter and the collector of the transistor Tr9. The second modulation waveform shaping circuit 33 constitutes the same circuit arrangement as the first modulation wave form shaping circuit and includes a capacitor C3b, resistors R13b, Rl4b and Rlb, a transistor Tr10 and a capacitor C4b. The outputs of both the modulation waveform shaping circuits 32 and 33 are coupled, respectively, to diodes D4 and D5 of theoutput circuit 35. The soundsignal oscillating circuit 34 constitutes an astable multivibrator including transistors Tr11 and Tr12, resistors R16-R19 and capacitors C5a and C5b. The output of theastable multivibrator 34 is coupled on the diodes D4 and D5. The diode D4 is coupled through a firstDC blocking circuit 351 consisting of a blocking capacitor C6 and a resistor R20 to afirst filter circuit 353 consisting of resistors R22, R23, R24 and capacitors C8 and C9. The diode D5 is coupled through a secondDC blocking circuit 352 including a blocking capacitor C7 and a resistor R21 to asecond filter circuit 354 consisting of resistors R25, R26 and R27 and capacitors C10, and C11. The outputs from both the filter circuits are supplied, respectively, toelectric amplifiers 44L and 44R of thesound reproducing device 23.

The dual channelsound reproducing device 23 is a car stereo tape player having a left channel including a reproducinghead 40L, apreamplifier 41L, asound volume adjuster 42L, alevel setting resistor 43L and theelectric amplifier 44L; a right channel including a reproducinghead 40R, a preamplifier 41R, alevel setting resistor 43R and theelectric amplifier 44R; a series connection of anelectric power switch 45, adiode 46 and asmoothing circuit 47; and a tape drive motor 48 connected between ground and a junction present between thepower switch 45 and adiode 46. Thediode 46 is provided to prevent a supply of an output from the drive circuit to the motor 48 when thepower switch 45 is opened. The collector of each of transistors Tr4, Tr5 and Tr6 in thedrive circuit 30 is connected in a forward direction to a diode D2. The diode D2 is provided to prevent a supply of a DC current into thedrive circuit 30 when thepower switch 45 is thrown in.

Explanation is now made of the circuit operation of the speed alarm system.

First of all, thelevel setting adjuster 26 is set to a control speed, 80 km/h for example, as stipulated by the Road Traffic Law. The generator generates an AC output voltage nearly proportional to a travelling speed of an automobile, as shown in FIG. 3. The AC output voltage so generated is set, through resistors R3 and R7 of thelevel setting adjuster 26, to a predetermined level, rectified in a rectifyingcircuit 28 consisting of a diode D1 and a capacitor C1 and supplied through a resistor R9 to the base of the transistor Trl of theSchmitt circuit 29.

Suppose that the travelling speed of the automobile exceeds a setting speed and the output voltage of the rectifying circuit reaches a predetermined potential.

Then, the transistor Trl is turned ON and the transistor Tr2 is turned OFF. When the collector potential of the transistor Tr2 is raised to cause the transistor Tr3 to turn ON, the transistors Tr4, Tr5 and Tr6 of thedrive circuit 30 are operated. This causes a DC power to be supplied through a resistor R10 to analarm signal generator 22 and through diode D2 to the smoothingcircuit 47 of thesound reproducing device 23. When the DC power is supplied to thealarm signal generator 22, theastable multivibrator 31 is operated to cause signals opposite in phase to each other, as shown in FIGS. 4a and 4b, to be generated from the two output terminals of the astable multivibrator. These signals are shaped, by the first and second modulation waveform shaping circuits 32 and 33, to wave forms shown in FIGS. 40 and 4d. The outputs supplied through resistors R31 and R32 from the first andsecond modulation circuits 32 and 33 modulate output signals supplied through diodes D4 and D5 from theastable multivibrator 34. The output signals of theastable multivibrator 34 and the modulated signals are respectively shown in FIGS. 4e to 4g. The DC portions of the modulated signals are eliminated at the first andsecond blocking circuits 351 and 352 to obtain signals as shown in FIGS. 4H and 4l. These modulated signals are filtered at the first and second filter circuits to obtain wave forms shown in FIGS. 4j and 4k. Since the two modulated signals or alarm signals so filtered are obtained through modification of the output signals of theastable multivibrator 34 by the signal alternately generated from the two output terminals of theastable multivibrator 31, these alarm output signals are shifted in phase from each other. When these alarm signals, after amplified by theamplifiers 44L and 44R of the stereo player set, are supplied to the left andright channel speakers 24R and 24L intermittent sounds shifted intime from each other are generated from the left and right speakers to alarmingly provide stereophonic alarm signals. At this time, anindication circuit 37 receives intermittent signals alternatively from the first andsecond modulation circuits 32 and 33 to cause the transistors Tr13 to effect an on-off operation. This causes alamp 38 connected to the transistor Tr13 to flicker in synchronization with the alarm sounds of speakers, thereby too attracting the attention of the driver.

With the above sound reproducing system, when a cartridge is incorporated into the car stereo set to cause the power source switch 45 of the stereo set to be thrown in to permit the car stereo set to be played, the alarm sounds are generated from the speakers together with performance sounds where the alarm device is operated. Suppose that the car stereo set is not in a playing position when the alarm device is operated, thedrive circuit 30 feeds DC electric powers to the amplifiers of the car stereo set, where they are amplified. The amplified alarm signals are supplied to the speaker, and alarm sounds are generated from the speakers.

The alarm device is so designed that its sound volume is varied according to the sound volume set up by the adjuster of the car stereo set. with a predetermined difference in level left therebetween. That is, an alarm sig nal current is flowed through resistors R24 and R27 of the filter circuit andresistors 43L and 43R into the soundvolume adjusting resistors 42L and 42R to cause a voltage drop to take place across the adjustingresistors 42L and 42R andresistors 43L and 43R. The voltage drop across theresistors 42L and 42R and 43L and 43R provides an input voltage to theamplifiers 44L and 44R. Therefore, adjustment of the soundvolume adjusting resistors 42L and 42R causes the level of the level alarm signal to be varied at the input terminal of theamplifiers 44L and 44R. When the sound volume is so adjusted, alarm sounds are generated from the speaker with a predetermined difference in level be tween the performance signal and the alarm signal. The difference in level between the signals, or sound volumes, is provided by selecting a desired value of theresistors 43L and 43R. The sound volume level relation between the alarm sound and the performance sound is shown in FIG. 5.

The alarm system is so designed that an operational accuracy is not varied relative to a temperature variation. A circuit device using a semiconductor element is generally susceptible to influence due to a temperature variation. For this reason, such circuit device is provided with a temperature compensating means. However, provision of the temperature compensating means makes the circuit of the device intricate in design and, furthermore, an expensive circuit device results. According to the alarm system of this invention, a temperature compensation is made by a generator having an opposite temperature characteristic to that of a semiconductor and no particular temperature compensating means is necessary. That is, when a temperature variation takes place at the AC generator, an output level of the AC generator whose generating voltage is dropped with a temperature rise is varied in an opposite direction to a detection level of the Schrnitt circuit whose temperature is varied and the output variation of the semiconductor circuit device is cancelled by the output variation of the generator. The device as a whole has, in effect, a constant temperature characteristic.

Let us now explain the above alarm system as incorporated into an automobile.

As shown in FIG. 6, aspeed alarm device 50 is mounted to a dash-board 51 at the front of the drivers seat of the automobile, and electrically coupled to asound reproducing device 23, a car stereo set for example, adjacent to thedevice 50. The output line of the car stereo set 23 is connected to twospeakers 24L and 24R disposed at the rear of a backward seat of the automobile. The speed alarm device, as shown in FIG. 7, is coupled to the output of agenerator 56 for generating an electric power through rotation of theengine 54. Thegenerator 56 is connected to aspeedometer 57. Thegenerator 56 is mechanically connected to a shaft of a flexible cable 55 towardspeedometer 57.

Thespeed alarm device 50 has ametal fitting 61 by means of which, as shown in FIG. 8, anindication window 58 is mounted at the front of acasing 59 and an operatingknob 60 is secured to the bottom of the easing 59. A printedcircuit board 63, onto whichelectrical parts elements 62 constituting an electrical circuit shown in FIG. 2 of the device are mounted, is accommodated into thealarm device 50 as shown in FIG. 9. The rear end of thesubstrate 63 is inserted into agroove 73 provided betweenprojections 71 and 72 projecting from the back face of thecasing 59. Apreset switch 64 of the speed setting device is provided at the forward bottom portion of the casing. Ashaft 65 extends through the bottom of the casing and towards the outside of the casing. An operatingknob 60 is fitted over an operatingsection 66 of theshaft 65. Thepreset switch 64 is secured fixedly to the bottom of the case by afastening nut 67a and anut 67b. Theprint substrate 63 is arranged on the top of thespeed setting switch 64 and electrically connected to a switch contact and an electrical circuit of the print substrate. A rotatablelong shaft 68 is connected integrally to theshaft 65 of thespeed setting switch 64 and extends vertically in thecasing 59. Arotatable drum 69 is mounted to, and rotated with, theshaft 68. Therotatable drum 69 is made of, for example, a transparent or semitransparent synthetic resin, and characters, such as 40 km/h, 60 km/h, 80 km/h etc., representative of respective control speeds are printed on the outer periphery of thedrum 69. A doughnut-shapedcavity 74 is formed within thedrum 69. An indication lamp is disposed opposite to anindication window 58 and within thecavity 74. The indication lamp is mounted on theprint substrate 63 and electrically connected to the electrical circuit of the print substrate.

With the above structure, when the operatingknob 60 is rotated stepwise, thespeed setting switch 64 is switched to cause therotatable drum 69 to be rotated to permit the characters of the control speeds visually observed from theindication window 58 to be varied. When the operatingknob 60 is stopped upon appearance of a desired character, thealarm device 50 is set to a speed control indicated by the character.

A front covering 75 having theindication window 58 is formed from synthetic resin, plastics, for example, and detachably mounted to thecasing body 59. Agroove 76 is provided in the upper inner surface of thefront cover 75 and aprojection 77 is provided on the lower outer surface of the front covering. The upper forward end of thecasing body 59 has asection 78 bent into L-shape in cross section and an engagingpawl 79 at the lower forward end of the casing body. The front covering 75 is mounted to thecasing 59 by engaging the forward end of thebent section 77 with thegroove 76 while engaging theprojection 77. The engagingpawl 79 is located in therecess 80 provided in the bottom of thecasing 59, as shown in FIG. 10, in a manner that theshaft 65 of the preset switch extends through the recess and the pawl. The engagingpawl 79 consists of awasher portion 81, a leg portion and a pawl. When thefront cover 75 is mounted to thecasing 59, the pawl 83 is snap-fitted on the projection to hold the front covering 75 in position. When the pawl 83 is unsnapped from the projection, thefront cover 75 is removed from thefront covering 75.

Let us now explain the method in which thespeed alarm device 50 is incorporated into the dash-board 51 of an automobile.

As shown in FIG. 11, abracket 85 has aframe 86 and aside plate 87 provided on one side of the frame. Twoopenings 88 are provided one at one side and one at the other side of theframe 86. At the top surface of the frame are formed threeopenings 89. Threeopenings 90 are provided at theside plate 87. When thealarm device 50 is mounted through thebracket 85 to the bottom portion of the dash-board of the automobile,

thebracket 85 is mounted to the lower portion of the dash-board, as shown in FIG. 12, by abolt 91 passed through the central opening provided at the top surface of thebracket 85. Thebracket arm 61 is mounted to one side of thebracket 85 in a manner to permit ahole 61a of the bracket arm to align with theopening 88 of the bracket. Thealarm device 50 is secured to thebracket 85 by bolt and nut means inserted into the aligned hole and opening.

As shown in FIG. 13 the alarm device is mounted through thebracket 85 to the dash-board 51 by inserting a bolt into the opening of theside plate 87 of thebracket 85.

What we claim is:

1. A speed alarm system mounted on an automobile with a car stereo device including an AC generator for generating an output voltage proportional in magnitude to a travelling velocity of the automobile comprising; a speed setting device coupled to the AC generator and being selectively set to a predetermined velocity; a speed limiting detector including a Schmitt circuit coupled to the speed setting device and being operated by the output thereof when the travelling velocity of the automobile reaches said predetermined velocity; an alarm signal generator coupled to the speed detector and adapted to be operated by the output of the speed detector to generate two intermittent alarm signals shifted in phase from each other; and means for coupling the alarm signal generator to a car stereo device installed in the automobile to deliver the two alarm signals respectively from the car stereo device whether or not it has been activated prior to the attainment of said predetermined velocity.

2. The speed alarm system according to claim 1 in which said speed detector comprises said Schmitt circuit operated when an output voltage from the speed setting device reaches a predetermined potential, and a drive circuit adapted to be operated by the action of the Schmitt circuit.

3. The speed alarm system according to claim 1 in which said coupling means includes a terminal coupling the output of the speed limiting circuit to a load circuit of the car stereo device to cause it to be operated by the output of a drive circuit included in said speed detector even when a power source switch is opened.

4. The speed alarm system according to claim 1 in which said alarm signal generator comprises an astable multivibrator for alternately generating output signals from its two terminals; two modulation wave form shaping means connected respectively to the two terminals of the astable multivibrator; an alarm signal oscillator for oscillating alarm signals having a predetermined frequency; and an output circuit for modulating the outputs of the two modulation wave form shaping means with these output signals of the alarm signal generator divided into two routes and smoothing the modulated signal.

5. The speed alarm system according to claim 1 in which said speed setting device comprises a plurality of resistors having respective resistances accurately set according to respective control speeds. and a changeover switch having contacts connected respectively to the associated resistors.

6. The speed alarm system according toclaim 2 in which the drive circuit is coupled through a first backward current blocking diode to the load circuit of the car stereo device.

7. The speed alarm system according to claim 6 in which said car stereo device includes a stereo tape player comprising a motor and a dual channel sound reproducing circuit having a second backward current diode connected between the motor and the sound reproducing circuit and one end of the first backward current blocking diode connected between the second diode and the reproducing circuit.

8. The speed alarm system according to claim 1 in which said car stereo device is coupled to the sound volume adjuster and includes a sound reproducing circuit having an electric power amplifier to which the output of the alarm signal generator is received, and a level setting impedance connected between the sound volume adjusting device and a junction connected to the electric power amplifier and supplied with the output of the alarm signal generator, said level setting impedance being designed to generate at all times alarm sounds at a volume increased by a predetermined level. l t l

Claims (8)

1. A speed alarm system mounted on an automobile with a car stereo device including an AC generator for generating an output voltage proportional in magnitude to a travelling velocity of the automobile comprising; a speed setting device coupled to the AC generator and being selectively set to a predetermined velocity; a speed limiting detector including a Schmitt circuit coupled to the speed setting device and being operated by the output thereof when the travelling velocity of the automobile reaches said predetermined velocity; an alarm signal generator coupled to the speed detector and adapted to be operated by the output of the speed detector to generate two intermittent alarm signals shifted in phase from each other; and means for coupling the alarm signal generator to a car stereo device installed in the automobile to deliver the two alarm signals respectively from the car stereo device whether or not it has been activated prior to the attainment of said predetermined velocity.

2. The speed alarm system according to claim 1 in which said speed detector comprises said Schmitt circuit operated when an output voltage from the speed setting device reaches a predetermined potential, and a drive circuit adapted to be operated by the action of the Schmitt circuit.

3. The speed alarm system according to claim 1 in which said coupling means includes a terminal coupling the output of the speed limiting circuit to a load circuit of the car stereo deviCe to cause it to be operated by the output of a drive circuit included in said speed detector even when a power source switch is opened.

4. The speed alarm system according to claim 1 in which said alarm signal generator comprises an astable multivibrator for alternately generating output signals from its two terminals; two modulation wave form shaping means connected respectively to the two terminals of the astable multivibrator; an alarm signal oscillator for oscillating alarm signals having a predetermined frequency; and an output circuit for modulating the outputs of the two modulation wave form shaping means with these output signals of the alarm signal generator divided into two routes and smoothing the modulated signal.

5. The speed alarm system according to claim 1 in which said speed setting device comprises a plurality of resistors having respective resistances accurately set according to respective control speeds, and a change-over switch having contacts connected respectively to the associated resistors.

6. The speed alarm system according to claim 2 in which the drive circuit is coupled through a first backward current blocking diode to the load circuit of the car stereo device.

7. The speed alarm system according to claim 6 in which said car stereo device includes a stereo tape player comprising a motor and a dual channel sound reproducing circuit having a second backward current diode connected between the motor and the sound reproducing circuit and one end of the first backward current blocking diode connected between the second diode and the reproducing circuit.

8. The speed alarm system according to claim 1 in which said car stereo device is coupled to the sound volume adjuster and includes a sound reproducing circuit having an electric power amplifier to which the output of the alarm signal generator is received, and a level setting impedance connected between the sound volume adjusting device and a junction connected to the electric power amplifier and supplied with the output of the alarm signal generator, said level setting impedance being designed to generate at all times alarm sounds at a volume increased by a predetermined level.

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