Abstract:
A motorcycle audio system is provided with circuitry to toggle the helmet mounted microphone of both the driver and the passenger on and off by use of the PTT (push to talk) switches commonly provided for use with a CB radio. Activation of a PTT immediately causes both microphones “on” regardless of their prior state. If the PTT is released during a predetermined short period, the microphones are turned off only if they were on prior to activation of the PTT and remain on only if they were off prior to activation. If the PTT is released after the predetermined period, the microphones remain on only if they were on prior to activation.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to the control of intercom systems for motorcycles and other vehicles.  
           [0002]    Intercoms allowing the driver and a passenger of a motorcycle to communicate with each other by means of speakers and microphones mounted in their helmets are well known. It is also well known to use the same speakers and microphones to allow the driver and the passenger to communicate with others by means of a CB radio, and/or to utilize the speakers to allow them to listen to entertainment audio which may be selected from audiotape players, CD players, MP 3 players and AM/FM radio. An example of the controls for such a multifunction audio system is described in U.S. Pat. No. 6,225,584. Voice actuated (VOX) circuits such as those described in U.S. Pat. No. 4,754,486 are often included in such multifunction audio systems to reduce or eliminate the entertainment signal to the speakers when one of the microphones or the CB receiver is actuated.  
           [0003]    When using a multifunction system of the type described above, it will often be considered inconvenient to have the intercom on only when communication is desired. However, leaving the intercom in the “on” state can result in the undesired transmission of sounds originating from one of the users or from the environment. Such undesired transmissions can be annoying in themselves and may also degrade the entertainment audio by undesired activation of the VOX circuitry. Safety is a concern if the intercom volume control is used to eliminate undesired transmissions, since this requires the driver to remove a hand from the handlebars to access the volume control, which is usually located in the center tank area of the motorcycle. This can result in the driver having one hand removed from the handlebars for a significant amount of time.  
         SUMMARY OF THE INVENTION  
         [0004]    Because a multifunction audio system for a motorcycle may include a CB radio, the controls for such a system usually include PTT (push to talk) switches conveniently located for activation by the driver and the passenger. The present invention provides means for switching the helmet mounted microphones of both the driver and the passenger both on and off by use of one of the PTTs. Regardless of their prior state (“on” or “off”), activation of a PTT immediately causes both microphones to be “on.” If the PTT is released during a predetermined short period of time (for example, 0.5 sec), the microphones are turned “off” if they were “on” before activation of the PTT and remain “on” if they were “off” prior to the activation of the PTT. If the PTT is released after the predetermined period of time, the microphones remain on only if they were “on” before activation. The intercom can thus be activated and deactivated by short activation of the conveniently located PTTs. This permits the driver and the passenger to conveniently communicate with each other, while avoiding undesired transmissions over the intercom when communication is not desired. Since this is accomplished by activation of the PTTs that the users are accustomed to using for CB communication, the present invention avoids having to locate another communication control switch in the limited space available on a motorcycle and avoids requiring the user to decide upon and find the proper control for the desired type of communication. This enhances the safety of the operation of the motorcycle by eliminating or minimizing the time that the driver will not have both hands on the handle bars.  
           [0005]    A motorcycle communication system equipped with the controller of the present invention will permit conventional push-to-talk operation of the intercom if the CB radio is turned off, or is not present. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a functional block schematic of a multifunction audio system incorporating the present invention.  
         [0007]    [0007]FIG. 2 is a schematic of one embodiment of the intercom control of FIG. 1.  
         [0008]    FIGS.  3 - 4  make up a flow chart of the logic of a second embodiment of the intercom control of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0009]    [0009]FIG. 1 illustrates a multifunction audio system for use by the driver and a passenger of a motorcycle which includes driver&#39;s helmet mounted speakers  2  and passenger&#39;s helmet mounted speakers  4 , both of which are capable of accepting inputs from the driver&#39;s microphone  6 , the passenger&#39;s microphone  8 , the CB radio  10  and the entertainment system  12 . The speakers  2  and  4  and microphones  6  and  8  are conventionally mounted in helmets worn by the driver and passenger respectively. Speakers mounted on the chassis of the motorcycle may, however, supplement or replace such helmet mounted speakers. The microphones  6  and  8  are connected to the speakers  2  and  4  by an intercom circuit  32  which can be activated and deactivated by means of a conventional switch  14 . The entertainment system  12  may comprise an AM/FM radio, an audiotape player, a CD player, a MP3 player or any combination thereof. A VOX attenuator  16  is conventionally provided to reduce or eliminate the entertainment signal to the speakers  2  and  4  when either the CB receiver  18  or one of the microphones is activated.  
         [0010]    An audio control  20  is conventionally mounted on a handlebar  22  of the motorcycle. The audio control  20  includes a driver&#39;s PTT  24  conventionally disposed close to the handlebar  22  so that it can be conveniently activated by the driver. A passenger&#39;s PTT  26  is also provided. Both the driver&#39;s PTT  24  and the passenger&#39;s PTT  26  are conventionally provided to activate the transmitter  28  of the CB radio  10 .  
         [0011]    The intercom controller  30  of the present invention is electrically connected to the driver&#39;s PTT  24  and the passenger&#39;s PTT  26  so as to be responsive to the activation of either PTT. The intercom controller  30  is also connected to the intercom circuit  32  so as to be capable of activating and deactivating that circuit. It has been found convenient to connect the intercom controller  30  to the portion of the intercom circuit  32  comprising the output cable  34  from the driver&#39;s microphone  6  and output cable  36  from the passenger&#39;s microphone  8 . The intercom controller  30  may, however, be connected to the intercom circuit  32  at any point that would not interfere with signals to the speakers  2  and  4  from either the receiver  18  or the entertainment system  12 . Unless overridden by the opening of switch  14 , when either PTT  24  or PTT  26  is activated, intercom controller  30  operates to activate intercom circuit  32  if it was inactive prior to activation of the PTT and will have no immediate effect if the intercom circuit  32  was active prior to activation of the PTT. If the activated PTT is then released during a predetermined short period of time, the intercom controller  30  allows the intercom circuit  32  to remain active if, but only if, it was inactive prior to the activation of the PTT. If the activated PTT is released after said predetermined period, the intercom controller  30  permits the intercom circuit  32  to remain active only if it was active prior to the activation of the PTT. The intercom circuit  32  can thus be toggled between the active and inactive states by short activations of the PTTs  24  and  26  without interfering with the operation of the CB radio. To accomplish this objective, it has been found preferable to set said predetermined period of time at between 0.1 seconds and 0.75 seconds, approximately 0.5 seconds being best for most users. In some cases, however, it may be found desirable to set said predetermined delay for as long as 2 seconds.  
         [0012]    [0012]FIG. 2 is a detailed schematic of one embodiment of the intercom controller  30 . The controller  30  is powered by a motorcycle&#39;s conventional electrical system; an externally fused 13.8 volt DC source. This source voltage is applied to the controller  30  through series wired diode D 1  and parallel wired capacitor C 1  for the purpose of power supply filtering. This creates 13.2 volts for the controller  30  while diode D 1  also provides reverse polarity protection. U1 is a LM339 quad comparator with two of it&#39;s comparator stages spared in this design. Both U1-A and U1-B are given the same inputs and therefore react to input changes concurrently. The negative input  37  of U1-A (pin  4 ) and the negative input  39  of U1-B (pin  10 ) are referenced with 0.97 volts via voltage divider R 2 /R 5 . Positive input  41  of U1-A (pin  5 ) and positive input  43  of U1-B (pin  11 ) are created by voltage divider R 1 /R(CB) through blocking diode D 2 , from PTT switches  24  and  26 . R(CB) is the internal resistance of the PTT detection circuit which is a part of a conventional motorcycle CB radio, and thus external to the controller  30 . Capacitor C 2  functions with resistor R 3  to provide switch debounce and pulse stretching. When both PTT switches  24  and  26  are open (not activated), U1&#39;s positive inputs are 1.8 volts, which is greater than negative inputs 0.97 volt reference. Due to the comparator&#39;s open collector outputs design, open circuit to ground is present at outputs  38  and  40  (pins  2  and  13  respectively). Pull-up resister R 3  causes a logic 1 at U2-A input  42  (pin  1 ) and U2-C input  44  (pin  8 ). When either PTT  24  or PTT  26  is closed U1&#39;s positive inputs are 0.6 volts, which is less than negative inputs 0.97 volt reference. Due to the comparator&#39;s open collector outputs design, closed circuit to ground is now present at U1 outputs  38  and  40  (pins  2  and  13 ). Logic 0 will be applied to U2-A input  42  (pin  1 ) and U2-C input  44  (pin  8 ). A base biasing current is thereby provided from U1-B output  40  to transistor Q 1 .  
         [0013]    U2 is a CD4093 two input NAND Schmitt Trigger quad gate. U2-A/U2-B forms a one-shot timer output to U2-C input  46  (pin  9 ) when initiated from U1-A output  38  (pin  2 ) by PTT switch closure. A pulse at U2-A output  48  (pin  3 ) of approximately 0.5 sec. results from RC network resister R 4 , capacitor C 3  values and the chips Schmitt Trigger input design. If the activated PTT switch is re-opened during this 0.5 sec. window, a logic 1 would be presented to both NAND gate U2-C inputs  44  and  46  (pins  8  and  9 ), and the output of U2-C at  48  (pin  10 ) is logic 0. U2-D forms an inverter, it&#39;s output a logic 1 at  64  (pin  10 ) applies a clock pulse to U3 at  58  (pin  11 ). U 3  is a CD4013 dual type D flip flop with one of the flip flop stages spared in this design and it is configured to provide a toggle at it&#39;s output. The primary connection to U3 are shown in FIG. 2 with reference numbers  50 ,  52 ,  54 ,  56 ,  58 ,  60  and  62  referring to pins  7 ,  8 ,  9 ,  10 ,  11 ,  12  and  14  respectively. Not shown, pins  1 ,  2  and  13  of U3 have no connection, pins  3 ,  5  and  6  are grounded and pin  4  is connected to the positive voltage line from diode D 1 . On initial energization (motorcycle ignition turn on), the combination of capacitor C 4  and resister R 8  provide a pulse to  52  (pin  8 ), causing the utilized circuit of U3 to latch it&#39;s output at  60  to logic 0. This causes the microphones to be turned on at motorcycle start up. U3 output state at  60  toggles on rising edge clock pulse at  58  from U2-D output  64 . Q 1  is a 2N3906 PNP transistor used as a switch. It is forward biased by a logic 0 caused by open collector ground from U1-B output  40  —OR— by U3 output  60 . Diode D 3  provides this OR circuit. When Q 1  is forward biased it&#39;s collector current will energize both relay coils  66  and  68 . D 4  suppresses back emf (electro motive force) caused when the relays de-energize (drop out).  
         [0014]    In another embodiment of my invention, the intercom controller  30  comprises a synchronous microcontroller which operates as shown in FIG. 3.  
         [0015]    Many other changes and modifications in the embodiments of the invention can also be carried out without departing from the scope thereof.