Abstract:
A wireless microphone system for a vehicle mounted surveillance system including an audio/video recorder, which may be automatically activated. Upon activation by the surveillance system, an ultrasonic transmitter generates an ultrasonic signal which is received by a portable wireless microphone to activate a radio transmitter. The radio transmitter generates a radio signal including audio information which is received by the surveillance system and recorded.

Description:
[0001]    This application claims the benefit of a prior filed, co-pending application Serial No.  60 / 323 , 478  filed Sep. 19, 2001, entitled AUTOMATICALLY ACTIVATED WIRELESS MIC FOR IN-CAR VIDEO SYSTEM. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention relates to the automatic activation of microphones for surveillance systems and, more particularly, to an automatically activated wireless microphone for use with a vehicle mounted surveillance system including a video camera and recorder used by law enforcement personnel to record traffic stops and crime scenes.  
           [0003]    In law enforcement, there are many commercially available vehicle mounted audio and video surveillance systems which provide an audio and video record of a traffic stop. An example of such systems is set forth in U.S. Pat. Nos. 4,789,904 and 4,949,186. These surveillance systems provide an audio and video record which may be used for investigation and trial of an offender, and oftentimes eliminate any doubt as to the occurrences at a traffic stop or a crime scene. Typically a video camera and recorder are mounted in the vehicle and a clip-on wireless microphone is worn by the police officer for the purpose of transmitting audio signals to the recorder when the officer leaves the vehicle.  
           [0004]    One problem with these systems is that the officer may forget to turn on the microphone. If this occurs, no audio is recorded for the stop, which may make the video recording useless as a record of the event or arrest.  
         SUMMARY OF THE INVENTION  
         [0005]    It is, therefore, a primary object of the present invention to provide a wireless microphone in combination with a vehicle mounted surveillance system, wherein the microphone is automatically activated when the surveillance system begins recording.  
           [0006]    Another important object of the present invention is to provide a wireless microphone in combination with a vehicle mounted surveillance system as aforesaid, wherein the microphone is automatically activated inside the vehicle before the officer leaves the patrol car to investigate or issue a citation.  
           [0007]    Yet another important object of the present invention is to provide a wireless microphone in combination with a vehicle mounted surveillance system as aforesaid, wherein the microphone is automatically activated when the emergency lights or siren of the patrol vehicle are turned on.  
           [0008]    Still another important object of the present invention is to provide a wireless microphone in combination with a vehicle mounted surveillance system, wherein an activation signal at ultrasonic frequencies is automatically transmitted within the patrol car to initiate operation of the microphone when the surveillance system is activated, thereby assuring that an audio recording will be made.  
           [0009]    Yet another important object of the present invention is to provide such a transmitted activation signal at a frequency which precludes interference with other electronic equipment within the patrol vehicle.  
           [0010]    These and other objects of the invention are achieved by incorporating an ultrasonic detector into the wireless microphone circuitry to control activation of the transmitter, which typically transmits at VHF frequencies. An ultrasonic transmitter is interfaced with the surveillance system, and activated along with the emergency lights or when the surveillance system begins recording. The ultrasonic detector decodes the signal received from the ultrasonic transmitter and enables the VHF transmitter of the wireless microphone circuit.  
           [0011]    Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, a preferred embodiment of the present invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a diagrammatic illustration of the system of the present invention.  
         [0013]    [0013]FIG. 2 is a functional block diagram of the ultrasonic generator circuit.  
         [0014]    [0014]FIG. 3 is a functional block diagram of the VHF transmitter and ultrasonic decoder circuit.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    Turning more particularly to the drawings, FIG. 1 illustrates the primary components of the present invention. A vehicular video surveillance system  10  includes a video camera, audio and video recorder, monitor and control center which allows an audio and video recording to be made of traffic stops, chases, and field sobriety tests, for example. One such system  10  for law enforcement applications is the Eyewitness® in-car video system available from Kustom Signals, Inc. of Lenexa, Kans., USA. The video camera is typically mounted to the windshield near the rearview mirror in a patrol vehicle. The monitor and control center are mounted within easy reach of the driver&#39;s seat in the patrol vehicle such as in a center console above the rearview mirror adjacent the headliner. The audio and video recorder (VCR) is secured in a vault mounted in the trunk of the vehicle.  
         [0016]    A wireless microphone  12  is worn by the police officer to allow audio recording of events outside the patrol vehicle. Wireless microphone  12  includes a clip-on microphone  14 , a mic cord  16 , and a VHF transmitter and ultrasonic decoder  18 . The mic cord  16  also acts as an antenna for transmitter  18 . A green LED  20  on the transmitter  18  is illuminated when the transmitter  18  is on. When the battery voltage drops below a predetermined level, a red LED  22  illuminates to alert the police officer that the battery is low and the audio signal may not be received from the transmitter  18 . Transmitter  18  also includes a power switch  24  and a STANDBY/ON switch  26 .  
         [0017]    Power switch  24  controls power to STANDBY/ON switch  26  which controls power to transmitter  18 . Typically, at the beginning of a shift, the police officer moves switch  24  to the “ON” position. At the end of the shift the officer turns the transmitter  18  off by moving switch  24  to the “OFF” position. When switch  26  is in the “STANDBY” position, transmitter  18  is automatically activated when an ultrasonic signal is received by microphone  14  from the transducer  32  of an ultrasonic transmitter  28 . In the “ON” position, switch  26  supplies power from switch  24  to transmitter  18 .  
         [0018]    Ultrasonic transmitter  28  is connected to the recorder of system  10  via control line  30 . The ultrasonic transducer  32  emits an approximately 20 kHz ultrasonic signal. Transmitter  28  and transducer  32  may be mounted on or adjacent the control center in the patrol vehicle.  
         [0019]    In operation, when the emergency lights on a patrol vehicle are activated, video system  10  is automatically activated as is customary in systems of this type. This activates ultrasonic transmitter  28  which drives transducer  32  to saturate the interior of the patrol vehicle with an encoded ultrasonic signal. Microphone  14 , clipped to the officer&#39;s uniform, picks up the encoded ultrasonic signal which is decoded by the transmitter and ultrasonic decoder  18  to activate the VHF transmitter automatically. Any time the surveillance system  10  is activated, whether automatically or manually, ultrasonic transmitter  28  is enabled to transmit the encoded ultrasonic signal to wireless microphone  12  and automatically activate transmitter  18 .  
         [0020]    Referring to FIG. 2, a functional block diagram of the ultrasonic transmitter  28  is shown. Ultrasonic transmitter  28  operates from the vehicle&#39;s electrical system which is typically approximately 13.8 VDC using a 12 VDC battery input on line  30   b  with line  30   c  connected to vehicle ground. An input signal on control line  30   a  activates ultrasonic transmitter  28 , which may be activated by a voltage or a ground signal. A voltage condition is considered for voltages above approximately 8 volts, and a ground condition is considered for voltages below approximately 3 volts. Voltage/ground selection switch  33  is set to the desired activation signal. When an activation voltage is detected on control line  30   a  by voltage/ground selection switch  33 , an output signal on line  34  triggers a timer  36 . In response, timer  36  outputs a signal on line  38  to close generator switch  40  and thereby enable ultrasonic generator  42  by connecting it to a regulated power supply  46  via line  44 . Ultrasonic generator  42  outputs a signal on line  48  to power amplifier  50  which receives regulated power from power amplifier regulator  52  on line  54 . Power amplifier  50  has an output of approximately 1-3 watts to drive transducer  32  via lines  56  to output the ultrasonic signal.  
         [0021]    Timer  36  also outputs a control signal on line  58  to LED driver  60  which drives green LED  62  and red LED  64 . LED driver  60  energizes green LED  62  when ultrasonic transmitter  28  is powered on and is waiting for a signal command on line  58  from timer  36  to start transmitting. LED driver  60  energizes red LED  64  when it receives a signal on line  58  from timer  36  indicating that an ultrasonic signal is being transmitted. Timer  36  may be active for 5 to 10 seconds and may repeat the ultrasonic transmission two or more times to ensure activation of wireless microphone  12 . After completing its activation cycle, timer  36  resets and waits for the next activation voltage on line  30   a.    
         [0022]    Ultrasonic generator  42  operates approximately between 18-35 kHz and may operate at frequencies as high as 50 kHz. However, components for both transmitter  28  and wireless microphone  12  may be cost prohibitive at higher frequency ranges and may also cause and be more susceptible to RFI. Ultrasonic transducer  32  transmits a high amplitude ultrasonic signal that remains within the patrol vehicle to take advantage of bounce paths and effectively saturate the interior of the vehicle to ensure activation of the wireless microphone  12 .  
         [0023]    Referring to FIG. 3, a functional block diagram of the VHF transmitter and ultrasonic decoder  18  is shown and is powered by a 9 VDC battery  70 . Power switch  24  controls power to an ultrasonic decoder circuit  74  on line  76  which controls power to the VHF transmitter circuit  78 . STANDBY/ON switch  26  provides selective control of power to VHF transmitter circuit  78 . In the ON position, power is always supplied to VHF transmitter circuit  78  bypassing ultrasonic decoder circuit  74 .  
         [0024]    When switch  26  is in the STANDBY position, power is supplied to VHF transmitter circuit  78  when an ultrasonic signal is received by microphone  14  which is output on line  82  to microphone amplifier  84 . The signal is amplified and fed to high pass filter  86 . If the ultrasonic signal is of the correct frequency, it is passed to output line  88  from high pass filter  86 . The signal is rectified and triggers the power switch  90  to pass the 9 VDC power through switch  26  on line  92  to line  94 . Five-volt regulator  96  converts the 9 VDC input on line  94  to provide regulated 5 VDC power to the electronic components of VHF transmitter circuit  78 . When VHF transmitter circuit  78  is enabled, transmitter LED indicator  98  is activated and outputs a voltage on line  100  to illuminate green transmit LED  20 . If the voltage level of battery  70  falls below a predetermined level, battery low indicator  104  outputs a voltage on line  106  to illuminate red battery low LED  22 .  
         [0025]    Five-volt DC regulator  96  provides power on line  110  to a microphone audio input processor  112  which amplifies, compresses and encodes the input voice signal and may use a continuous tone coded squelch system (CTCSS). The CTCSS encodes a sub-audible tone on the modulated signal which is decoded by the receiver in the surveillance system  10  to open squelch and record the transmission. The CTCSS enables the surveillance system  10  to distinguish different transmissions on the same carrier frequency. The audio signal is applied to a VHF carrier signal by oscillator-modulator multiplier  114  the frequency of which is selectable by frequency selection switch  116 . Frequency selection switch  116  must be set to the same frequency of the audio receiver of the video surveillance system in order to be received and recorded. The output on line  118  is conditioned by VHF processor  120  which includes a multiplier, RF amplifier and low pass filter. The VHF signal is output on line  122  which is transmitted to the surveillance system using microphone cord  16  as an antenna.  
         [0026]    In operation, the officer turns on the VHF transmitter  18  by moving switch  24  to the ON position when starting his or her shift. Switch  26  is moved to the STANDBY position. When switch  26  is in the STANDBY position, and VHF transmitter  18  has been activated, it continually transmits signals from wireless microphone  12  to the surveillance system in the patrol vehicle. To turn off the transmitter  18 , the officer moves switch  24  to the OFF position and then back to the ON position which resets power switch  90  and the ultrasonic detector circuit  74 . The transmitter  18  is thereby reset and will respond to a subsequent ultrasonic activation. When the officer&#39;s shift is finished, he or she turns VHF transmitter power switch  24  to the OFF position.