Car&#39;s back-up alarm fitted with speech function
BACKGROUND OF THE INVENTION 
     The present invention relates to a car&#39;s back-up alarm, and particularly relates to a car&#39;s back-up alarm including a function which allows speech between the driver and person/persons outside the car at the time of the car moving backward. 
     In the case of driving a car in reverse gear, since such accidents as person/persons who was/were outside the car, particularly behind the car was/were hurt by the car have often occured, a construction of buzzing an alarm automatically at the time of its moving back is adopted. 
     However, the alarming for the backward moving with buzzing along may not assure the safety as it does not at all give notice of backward movement to both drivers and person/persons outside. 
     SUMMARY OF THE INVENTION 
     The subject of the present invention is to provide a back-up alarm which much more assures a better guiding of the auto body and safety by means of speech between the driver of the car and person/persons outside the car. 
     The means of the present invention comprises having provided a back/up switch which closes in linkage with a reverse gear operation member, having installed a handset at the driver&#39;s seat, having fixed a combination speaker/microphone in the rear of the auto body, and having placed a back/up switch and a handset in the electric circuit connecting the power to said combination speaker/microphone. 
    
    
     BRIEF DESCRIPTION OF DRAWING 
     FIG. 1 of the drawing is a diagram of the car&#39;s back-up alarm fitted with speech function. 
     FIG. 2 is a block circuit diagram. 
     FIG. 3 is an interrupted wave circuit diagram. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the FIG. 1, S 1  is a back/up switch which is placed in the electric circuit between the power source and the handset 6 installed at the driver&#39;s seat, such that the back/up switch S 1  is provided to be closed automatically upon engaging the reverse gear of transmission gear by means of an operation lever in the auto body. 
     A combination speaker/microphone 5 is fixed in the rear of the auto body to which speaker/microphone the handset 6 is connected. 
     In the FIG. 2, S 2  is a power switch which actuates the three modes as mentioned later. And, the inside of handset 6, as shown in FIG. 2, comprises an interrupted wave generating circuit 1, a pre-amplifier 2, a power amplifier 3, a duplexing circuit 4, and a power stabilizing wave circuit 7 and also a transmitter/receiver 6. S 3  is a handset switch of this device as will be described herein referring to FIG. 2. 
     Mode 1. In the case of speaking from the outside of the car and receiving it in the car-When power switch S 2  is thrown, the outside voice can always be listened to at the driver&#39;s seat. 
     Mode 2. In the case of speaking from the inside of the car and receiving (loud speaking) it outside of the car-When speaking over the handset 6 by keeping the transmit switch S 3  pushed, it can be loud spoken to the outside of the car. 
     Mode. 3. In the case of listening to the voice outside of the car at the same time of generating the alarm - Even when the power switch S 2  is not thrown, turning the back/up switch S 1  on actuates the circuit automatically for generating the sound of the alarm intermittently and, moreover, the voice outside of the car can be listened to at the driver&#39;s seat while the sound of the intermitted alarm is halted. At this stage, the Mode 2 condition above can be obtained by pushing the transmit switch S 3 , then speech can be done. The timing of speech/alarm is as shown in FIG. 3. 
     In the present invention, speech between the driver and person/persons outside the car can be made and, since every confirmation is made by sound, a high safety factor is obtained which is optimal for guiding a backward moving car, especially a sight seeing bus and garbage truck and gives a practical value.