Patent Publication Number: US-2021163100-A1

Title: Electromechanical shifting systems and methods

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/782,733, filed Feb. 5, 2020, which is a continuation of U.S. patent application Ser. No. 16/507,815, filed Jul. 10, 2019, now U.S. Pat. No. 10,589,822, which is a continuation of U.S. patent application Ser. No. 16/105,199, filed Aug. 20, 2018, now U.S. Pat. No. 10,392,078, which is a continuation of U.S. patent application Ser. No. 15/265,363, filed Sep. 14, 2016, now U.S. Pat. No. 10,093,391, which is a continuation of U.S. patent application Ser. No. 14/534,363, filed Nov. 6, 2014, now U.S. Pat. No. 9,540,071, which is a divisional of U.S. patent application Ser. No. 13/712,616, filed Dec. 12, 2012, now U.S. Pat. No. 8,909,424, claiming the benefit of U.S. Provisional Patent Application No. 61/712,636, filed Oct. 11, 2012, the contents of which are herein incorporated in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to bicycle components. In particular, the invention is directed to systems including wirelessly actuated bicycle components. The systems may include bicycle gear changers controlled by a wireless control signal, wherein the wireless control signal is generated by a bicycle control component. 
     One prior art electromechanical shifting system required a wireless transmitter and receiver to be on continuously. To conserve energy, a very low-power &amp; low-range transceiver was utilized. However, the low-power transceiver suffered from poor wireless performance. A more recent system requires a periodic beacon signal which will also always consume battery power. 
     There is a need for a highly reliable and more secure wireless control systems for bicycles. The invention satisfies the need. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention provides a control system for a component of a bicycle which may include a base part attachable to a bicycle and a movable part. The control system may also include a wake unit or wake sensor which causes at least a part of the bicycle component to become operational upon detecting accelerations, vibrations, and/or movement of the bicycle. 
     Another aspect of the invention provides aspect of the invention provides a control system for a component of a bicycle which may include a base part attachable to a bicycle and a movable part. The control system may also include an electric motor disposed on the electromechanical component and a control unit disposed on the electromechanical component for operating the electric motor to operate the electromechanical component, the control unit including a wireless receiver. The control system includes a wake sensor connected to the control unit, the wake sensor configured to cause the control unit and the wireless receiver to become operational in response to detected vibrations of the bicycle. 
     Yet another aspect of the invention provides a bicycle wireless control system for controlling a component on a bicycle. The wireless control system includes a slave control unit attached to the component and including a wireless receiver for communicating with a master control unit, the master control unit including a wireless transmitter that transmits a wireless command signal. The wireless control system also includes a wake unit attached to the slave control unit, the wake unit configured to detect vibration and cause the wireless receiver to become operational to receive the wireless command signal in response to the detected vibration. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a side view of a drop-bar style bicycle with wireless components installed thereon. 
         FIG. 2  is a view of a shifter/brake assembly with an integrated master control unit (MCU). 
         FIG. 3  is a flat type bar with shift units wired to a discrete control unit. 
         FIG. 4  is a rear gear changer according to an embodiment of the present invention. 
         FIG. 5  is a front gear changer according to an embodiment of the present invention. 
         FIGS. 6-9  are schematic views of a wireless communication/control system. 
         FIG. 10  is a wake/sleep timeline of a gear changer control unit (SCU). 
         FIG. 11  is a timeline of the SCU transmitter and receiver and the MCU transmitter and receivers. 
         FIG. 12  is a wake/sleep/TX timeline of the MCUs. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the invention will herein be described with reference to the drawings. It will be understood that the drawings and descriptions set out herein are provided for illustration only and do not limit the invention as defined by the claims appended hereto and any and all their equivalents. For example, the terms “first” and “second,” “front” and “rear,” or “left” and “right” are used for the sake of clarity and not as terms of limitation. Moreover, the terms refer to bicycle mechanisms conventionally mounted to a bicycle and with the bicycle oriented and used in a standard fashion unless otherwise indicated. 
     Referring to  FIG. 1 , a bicycle  20  with a drop-bar type handlebar is shown with a wireless communication/control system  22  in accordance with one embodiment of the invention. The wireless control system  22  includes at least one shift unit  24  (shifter) which may be mounted to a bicycle handlebar  26  attached to the bicycle. The bicycle  20  wireless control system  22  also may have one or both of an electromechanical front gear changer  28  and an electromechanical rear gear changer  30  mounted to the bicycle frame  32  part of the bicycle  20 . The gear changers  28 ,  30  may be derailleurs or internal gear hubs, for example. The control system  22  may be usable with other systems and/or components of the bicycle  20 , such as suspension components and systems, controllable seat posts, power meters, cadence meters, lighting, bicycle computers, and so on, in addition to gear changers or in the alternative to gear changers. For context, the bicycle  20  will typically have a drive assembly  33 , with one or more front chainrings  35  connected to a plurality of rear sprockets  37  by a chain  39  as is known in the art. 
       FIG. 2  shows a drop bar shift unit  24  in greater detail. The shift unit  24  may include a brake support bracket  34  mountable to a handlebar, a brake lever  36 , a shift lever  38 , (which is one form of a shift actuator, e.g., a button or the like), operatively coupled to a shift switch  40 , a front gear changer shift toggle button  42 , and a master control unit  44 , and a power source such as a battery  46 . Shift switch  40  may be actuated by any suitable actuator/device, such as a momentary contact button, for example. 
     Referring also to the embodiment of  FIG. 6 , the master control unit  44  may receive input signals from the shift switch  40  and front gear changer (FD) shift toggle button  42 , and also includes a CPU  48  provided in communication with the shift switch for processing the input signals, a memory component  50  in communication with the CPU, an optional indicator such as a LED  52  to display status signals generated by the CPU, and a wireless transmitter and receiver  54 . It will be noted that the term “transmitter and receiver”, as used herein may include a transceiver, transmitter-receiver, or radio, and contemplates any device or devices, separate or combined, capable of transmitting and receiving wireless signals, including shift signals or control, command or other signals related to some function of the component being controlled. 
     Shift units  24  may be supplied in pairs  24   a ,  24   b  and are typically installed on the handlebar  26 , or a similar component, with one shift unit located to be operated with the right hand and the other to be operated with the left hand. When two separate shift units are employed, there may be a pair of master control units (MCU)  44  in the system  22 , one in each of the two units  24   a ,  24   b . Shift units  24  may be positioned anywhere within reach of the user, and multiple units and or shift switches  40 , or the like, may be positioned thereon, such as in the type of bicycle known as a time trial bicycle which can have shift units on both the bars and bar extensions. 
     In one embodiment, for example, the CPU  48  used may be an Atmel ATmega324PA microcontroller with an internal eeprom memory and the transmitter and receiver  54  used may be an Atmel AT86RF231 2.4 GHz transceiver utilizing AES encryption and DSS spread spectrum technology supporting 16 channels and the IEEE 802.15.4 communication protocol. Other suitable CPUs and wireless transmitter and receivers are contemplated. 
     In one embodiment of the wireless control system  22 , the shift lever  38  on the right shift unit  24   a , when actuated, causes the generation of a shift signal corresponding to an upshift, which is actuatable by the rear gear changer  30 . The shift lever on the left shift unit  24   b , when actuated, causes the generation of a shift signal corresponding to a downshift, which is actuatable by the rear gear changer  30 . Upshift corresponds to a gear shift to a higher gear (e.g., smaller rear sprocket  37 ) and downshift corresponds to a gear shift to a lower gear (e.g., larger rear sprocket  37 ). A front shift actuator  42 , which may be in the form of a button, and is an optional element, may be provided on both shift units  24  and when operated, transmits a toggle front shift signal to toggle the front gear changer  28 . Therefore, each MCU  44  of each shift unit  24  can wirelessly transmit shift signals that are receivable and may be actuatable by each gear changer. 
     It may also be desirable to add a modifier actuator  56  to, for example, the shift unit  24 . A modifier actuator  56 , which may be in the form of a button, does nothing when operated alone, but when operated in combination with another actuator causes the generation of a different type of signal (i.e., not a shift signal). For example, when the shift lever  38  of unit  24   a  is pressed in combination with the modifier actuator  56  a “shift alignment inboard” or trim command, or the like, can be issued instead of an “upshift” command. The modifier actuator  56  may be located on the shift lever  38  and be in communication with the MCU  44 . 
       FIG. 3  shows another embodiment with the system  22  adapted to a flat-bar application. In this embodiment, right and left shift units  124   a ,  124   b  are provided. A shift junction box  58  may be connected by signal wires  60  to the right shift unit and left shift units  124   a ,  124   b . A single master control unit  144  may be located in the shift junction box  58  that receives signals from the left and right shift units  124   a ,  124   b  ( FIG. 8 ). The single master control unit  144  includes components similar to those of MCU  44  in the shift units  24 . Specifically, the MCU  144  includes a CPU  148  in communication with the left and right shift units  124   a ,  124   b , a memory component  150  in communication with the CPU, a transmitter and receiver component  154 , and a LED  152  to indicate operating conditions of the MCU  144 . A battery  146  provides power to the MCU  144  and a modification actuator  156  is provided to modify the operation of the MCU. 
     Although this flat-bar embodiment is shown with a shared single master control unit  144 , two master control units could be employed. Alternatively, junction box  58  and shared master control unit  144  could be employed in the drop bar version described above. Each of the shift units  124   a ,  124   b  may have a shift switch  140 , which is responsive to the shift levers  38  of shift unit  24  described above. 
     An embodiment of an electromechanical rear gear changer  30  (RD) is shown in  FIG. 4 . In general, electromechanical gear changers are known in the art. The present rear gear changer includes a power source  62  (battery), a motor unit  64 , and a gear changer control unit  66  (SCU or “slave control unit”). The gear changer control unit  66  ( FIG. 7 ) may include a CPU  68  to process signals/commands, and the like, a wake sensor  70  operatively connected thereto, a memory component  72 , a function button  74 , an indicator such as a LED  76 , an output  78  to send control signals to the motor unit  64 , and a transmitter and receiver  80  for sending and receiving wireless signals. The motor unit  64  receives and executes position trim commands and/or gear change commands from the gear changer control unit  66 . 
     An embodiment of an electromechanical front gear changer  28  (FD) is shown in  FIG. 5 . Like the rear gear changer described above, the front gear changer has a power source  82  (battery), a motor unit  84 , and a gear changer control unit  86  (SCU). The gear changer control unit  86  ( FIG. 7 ) may include a CPU  88  to process signals/commands and the like, a wake sensor  90  operatively connected thereto, a memory component  92 , a function button  94 , an indicator such as a LED  96 , an output  98  to control/operate the motor unit  84 , and a transmitter and receiver  100  for sending and receiving wireless signals, which may also be referred to as a gear changer transmitter and receiver. The motor unit  84  receives and executes position and/or gear change commands from the gear changer control unit  86 . In the illustrated embodiment, the front gear changer shifts between two chainrings. Alternatively, more than two chainrings are contemplated. The CPU  88  may also be configured to toggle shift the front gear changer  28  between two chainrings when the function button  94  is pressed then released. 
     Referring also to  FIG. 9 , while the rear gear changer  30  and front gear changer  28  is described as each having a gear changer control unit, a single shared gear changer control unit  102  could be employed. The shared gear changer control unit  102  shown is located in a gear changer junction box  104 , but could also be located within the rear gear changer  30  or front gear changer  28 . The shared gear changer control unit  102  may include a power source  184  (battery). The gear changer control unit  102  may include a CPU  188  to process signals from the MCU  144 , a wake sensor  190 , a memory component  192  coupled to the CPU, a function switch  194 , a LED  196 , and a transmitter and receiver  200  configured to send and receive wireless signals. 
     In one embodiment, the CPU  88  or  188  may be an Atmel ATmega324PA 8-bit RISC microcontroller with an internal eeprom memory. The transmitter and receiver  100 ,  200  may be an Atmel AT86RF231 2.4 GHz transceiver utilizing AES encryption and DSS spread spectrum technology supporting 16 frequency channels and the IEEE 802.15.4 communication protocol. 
     Channel Selection 
     It is possible to set the system  22  to one of a plurality of different selectable transmitter and receiver frequency channels to avoid crosstalk with other systems in the vicinity. A device may be designated in the system  22  to be the channel master. The channel master device may be the rear gear changer  30 . Prior to pairing devices, (i.e., the shift unit(s) and gear changer(s)), the rear gear changer  30  would be set to a particular transmitter and receiver frequency channel. This could be accomplished by pressing the function button  74  in a certain sequence, or could be accomplished with a selector switch, or could be accomplished by wireless communication with a device designed to perform such a task. It is considered that it would be within the skill of the ordinary artisan to accomplish such a task. 
     Pairing 
     The components of the wireless control system  22  are paired to enable wireless communication therebetween. Referring to  FIG. 2  and  FIGS. 4-7 , each Master Control Unit  44  has a unique “device ID” value and a “device type” value permanently stored in the MCU memory component  50 . The “device type” value indicates the type of device it is, for example: “right shifter unit” or “left shifter unit”. 
     For purposes of illustrating an embodiment of a pairing operation, an example with a front gear changer will be illustrated. It will be understood that the basic steps will be the same for a rear gear changer. The front gear changer  28  containing a gear changer control unit  86  (SCU) is paired with a shifter  24  containing a MCU  44  as follows. When a mode changing mechanism, which may be in the form of a function button  94  on the gear changer, is pressed for a pre-determined period of time, the SCU  86  of the gear changer enters or is converted to a pairing mode. The SCU  86  may slowly flash the LED  96  on the gear changer  28  to indicate that it is in pairing mode and turn on the SCU transmitter and receiver  100 . At this time, the receiver part of transmitter and receiver  100  in the SCU  86  scans transmitter and receiver channels, listening for transmitted signals, wherein listening may also be referred to as monitoring. Next, a shift lever/button  38  on the shift unit  24  with a MCU  44  is pressed and held, causing the MCU to transmit a repeating shift signal that contains the “device ID” and “device type” as part of the signal. When the SCU  86  in the gear changer  28  detects the repeating shift signal from a MCU  44 , the SCU may change the LED  96  to solid on. The SCU receiver part of transmitter and receiver  100  continues to listen for a repeating shift signal from the MCU  44  of the shifter for a pre-determined time period, which may be about two seconds. Once the SCU  86  of the gear changer  28  has determined that it has received a shift signal from the MCU  44  for the required period of time, the SCU exits the pairing mode and stores the “device ID” in the SCU memory component  92  in a space reserved for that “device type”. If the SCU  86  is the channel master in the system  22 , it will also send a signal to instruct the MCU  44  in the paired shifter  24  to operate on a particular channel. The shifter  24  and gear changer  28  are now paired and the gear changer&#39;s SCU  86  will respond to commands from the MCU  44  of the paired shifter. 
     The memory  92  of the SCU  86  of the gear changer  28  will only record one device ID for each device type. If a shifter  24  with a device id of “234” is paired with a rear gear changer  30 , and later another shifter  24  with the device ID “154” is paired with the rear gear changer, the SCU  72  memory value “234” in the “device type” space will be overwritten with the new value “154,” and the rear gear changer  30  will no longer respond to the shifter  24  of device ID “234.” 
     An embodiment of the wireless system  22  has right and left shifters  24   a ,  24   b ; each with a MCU  44 , and a front gear changer  28  and a rear gear changer  30 , each with a SCU  86 ,  66  ( FIGS. 6 and 7 ). Therefore, it will be understood that the pairing process will be repeated four (4) times for this embodiment. The rear gear changer  30  will be paired to each of the right and left shifters  24   a ,  24   b  and the front gear changer  28  will be paired to each of the right and left shifters. This creates a highly secure system because physical access is required to press the buttons on the components to pair the devices. Further, each gear changer  28 ,  30  will respond only to shifters with which they have been paired. If the operator verifies that each shifter  24   a ,  24   b  controls each of the gear changers  28 ,  30 , they can be confident that no unauthorized shifters have been paired. In an alternative embodiment, where a pair of shifters  124   a ,  124   b  shares a MCU  144  or the front and rear gear changers  28 ,  30  shares a SCU, the number of pairing steps will be reduced. 
     Wake Sensor 
     Conserving power on battery powered wireless devices is a design consideration and one contemplated by embodiments of the invention. If electronic devices are left on continuously, batteries tend to be quickly depleted. Therefore, various strategies may be implemented to conserve battery power. The MCU  44  connected with the shift unit(s)  24  may be configured to sleep, i.e. are in a relatively low-power state when the bicycle/system is inactive. During this time, the CPU  48  is in the low power state (sometimes known as standby or sleep mode) and the transmitter and receiver  54  is turned off. The MCU  44  only wakes (becomes fully powered and operational) and transmits signals when a switch or button is activated, otherwise it sleeps. 
     For example, the SCU  66  in the gear changer  30  may receive control signals from the MCU  44  or, in some cases, other SCUs. If the transmitter and receiver  80  is left on continuously, the battery  62  would be quickly depleted. The SCU  66  may include a wake unit  70  to determine and signal when the bicycle is being used. In one embodiment, for example, a SignalQuest SQ-MIN-200 or an Freescale Semiconductor MMA8451Q vibration sensor may be used as a sensor for the wake unit. When operating a bicycle, vibrations are caused by uneven road surfaces and drivetrain motion, which are easily detected by sensors (not shown). Other sensors could be used for the wake unit  70 , such as accelerometers or magnetic reed switches configured to detect magnets attached to moving elements of the bicycle  20 . When the bicycle  20  is operated, vibration or movement is detected and the wake unit  70  sends a wake signal to wake the SCU  66  ( FIG. 10 ). The SCU  66 , upon becoming fully powered and operational from a wake signal from the vibration sensor, becomes awake as long as it receives wake signals from the wake unit  70 . If wake signals are not received for a period that exceeds a predetermined sleep timeout value, the SCU  66  will go back to sleep. The duration of the sleep timeout may be about 30 seconds. 
     Transmitter and Receiver Timing 
     Power consumption can be further reduced by frequently turning transmitter and receivers  80 ,  100  on and off according to a predetermined or given period or cycle when the SCU  66 ,  86  is awake. When the SCU  66 ,  86  receives a signal from the wake sensor  70 ,  90  it enters an awake mode, becoming fully powered and operational. During the awake mode, the SCU  66 ,  86  turns the transmitter and receiver  80 ,  100  “on” to monitor for shift signals for a listen time A, which may be known as a listen mode, and then “off” for a wait time B, which may be known as a non-listen mode, to conserve energy as shown on timeline SCU on the chart. The total of one cycle of time A and B defines a given awake mode cycle period or awake mode cycle time. Typically, listen mode time A might be about 5 ms and wait time or non-listen mode B might be about 45 ms. In this state, the SCU transmitter and receiver  80 ,  100  is on (in listen mode) only about 10% of the time of the awake mode cycle time. 
       FIG. 11  shows the transmitter and receiver timing when shift signals are transmitted from the MCU  44  to the SCU  66 ,  86 . After a shift button  38  on the shift unit  24  is pressed, the MCU  44  enters a wake mode or state, waits for the channel to become clear, and transmits a series of duplicate control/shift signals if no other signals or noise is detected. Each of the duplicate shift signal has a duration time of C (about 1 ms) followed by a rest period time D (about 2 ms) and is repeated for a length of time, i.e., a message duration time F (about 100 ms). The message duration time F is chosen so that the shift signal from the MCU  44  will coincide with at least one time when the transmitter and receiver  80 ,  100  of the SCU  66 ,  86  is actively monitoring or listening, i.e. in a listen mode. In the example shown in  FIG. 11 , four control signals coincide with the time the SCU transmitter and receiver  80 ,  100  is in listen mode, as illustrated by the dashed lines. In other words, the gear changer transmitter and receiver actively listens for the shift signals from the shifter transmitter and receiver during a part of an awake mode cycle time and the shifter transmitter and receiver is configured to transmit the shift signals for a length of time which is greater than the awake mode cycle time to ensure that the gear changer transmitter and receiver will be in a state of active listening when a shift signal is being transmitted, wherein listening may also be referred to as monitoring. 
     When the SCU transmitter and receiver  80 ,  100  hears a shift or control signal, the SCU  66 ,  86  keeps the transmitter and receiver in listen mode, even if the detected signals are intended for another device. The SCU transmitter and receiver  80 ,  100  will stay in listen mode for a listen duration time G (about 20 ms) after the last signal is received before going back to sleep, i.e. the non-listen mode, to conserve power. It will be understood that the various timings illustrated herein are exemplary in nature. 
     During racing or large group rides it is inevitable that cyclists will be using a number of systems in detectably close proximity. Both the MCU  44  and SCU  66 , i.e.,  86 , may have special features to enable coexistence and ensure high reliability during crowded use. The MCU transmitter and receiver  54  has the ability to both transmit and receive signals. Prior to transmitting a wireless signal, the MCU  44  will listen to determine if other transceivers or devices are transmitting. These other transceivers may or may not be part of the instant system. When the MCU  44  hears other transceivers, prior to transmitting, it will observe the device ID(s) of the other signal(s) and count these devices until it sees a device repeated. When the MCU  44  determines that the channel is clear to transmit after hearing other transmissions, (i.e., any transmission that is not from a master control unit to which either of the SCUs  66 ,  86  is paired, wherein the other transmissions may be referred to as noise), it will begin transmitting a signal but may adjust the repeat interval by increasing the time between transmissions of the duplicate signals to avoid collisions with the other transmissions/noise. 
       FIG. 12  shows the interaction of three MCUs that attempt to transmit at the same time. The timeline MCU 1  shows the sleep (low power mode), wake (fully powered and including an actively monitoring mode), and transmit (TX) states of the first MCU. When a shift actuator is operated, the MCU wakes and pauses to listen for a quiet time (J) before transmitting signals (S 11 -S 14 ). Since no other signals or noise in this example were heard during quiet time J, S 11 -S 14  are repeated at a minimum repeat rate E (about 3 ms). When the MCU is awake, between transmitting signals, it listens for signals from other transmitters. 
     MCU 2  wakes from a TX command request and begins listening at time T 2 . After MCU 2  receives signal S 13  and S 14 , both from a common MCU, it determines that two devices will be transmitting and begins sending signals S 21 -S 25  at time T 3  and at a repeat rate E 2 , about 6 ms. MCU 2  transmits signal S 21  at time T 3  before S 15  of MCU  1 , thus “bumping” S 15 . MCU 1  was listening between S 14  and the planned S 15  signal and heard the signal S 21  from MCU 2 . MCU 1  then cancels S 15  and begins sending a new signal S 15 ′-S 18  starting at time T 4  at repeat rate E 2 . MCU 1  chooses to send signal S 15 ′ about 3 ms from T 3 , maintaining an interval between duplicate signals at a first interval or environmental signal repeat rate of about 3 ms. 
     MCU 3  wakes prompted by detection of a TX command request (shift signal) and begins listening at time T 5 . After MCU 3  receives signal S 24 , S 18 , and S 25 , where S 24  and S 25  are both from a common MCU, it determines that three devices will be transmitting and begins sending signals S 31 -S 35  at time T 6  and at a repeat rate E 3 , about 9 ms. Signal S 31  was transmitted prior to the planned signal S 19  of MCU  1 . MCU 1  was listening between signals S 18  and planned S 19  and received S 25  from MCU 2  and S 31  from MCU 3 . MCU 1  then cancels S 19  and begins sending a new signal S 19 ′-S 1 B starting at time T 7  at repeat rate E 3 . MCU 1  chooses to send signal S 19 ′ about 3 ms from T 6 , maintaining an environmental signal repeat rate of about 3 ms. Signal S 19 ′ was transmitted prior to the planned S 26  of MCU 2 , bumping that signal. MCU 2  was listening between signals S 25  and planned S 26  and received S 31  from MCU 3  and S 19 ′ from MCU 1 . MCU 2  then cancels S 26  and begins sending a new signal S 26 ′-S 2 A starting at time T 8  at repeat rate E 3 . MCU 2  chooses to send signal S 26 ′ about 3 ms from T 7 , maintaining an environmental signal repeat rate of about 3 ms. 
     Between S 28  and S 29 , MCU 2  observed that only S 34  was received from MCU 3  and determines that only two devices are now communicating. After S 29 , MCU 2  sends signals S 2 A-S 2 B at the increased repeat rate E 2 . Between S 34  and S 35 , MCU 3  observed that only S 29  was received from MCU 2  and also determines that only two devices are now communicating. After S 35 , MCU 3  sends signals S 35 -S 38  at the increased repeat rate E 2 . Between S 37  and S 38 , MCU 3  observed that no signals were received and it alone is communicating. After S 38 , MCU 3  sends signals S 38 -S 3 A at the increased repeat rate E. 
     Although the example above describes the transmitters adjusting their repeat intervals on the next transmit cycle, it may be desirable to wait more than one cycle before adjusting the repeat rate. This gives the transmitters more chances to notice other transmitters they might not have noticed on their initial tally. 
     There is a risk that two devices will attempt to send signals at exactly the same time. To reduce the possibility of collisions, the signal repeat rate E may be randomly varied by as much as plus/minus 1 ms, for example. 
     Also, the invention may include a method to maximize reliability thereof by maximizing the number of sent duplicate shift signals corresponding to the input signal in a given message duration time. If the repeat interval of the plurality of duplicate shift signals creates a situation where only a small number of duplicate shift signals can be transmitted, the system may increase the length of the message duration time to transmit a sufficient number of the duplicate signals at the increased interval rate. 
     Handling Duplicate Shift Commands 
     Because the MCU  44  of the shifter  24  sends the shift signal multiple times, the SCU  66 ,  86  of the gear changers  30 ,  28  need a method of discerning duplicate received shift signals from new shift signals. When the MCU  44  generates a shift signal it also generates a “count value” that is transmitted along with the device ID and device type. Each time a new shift signal is generated by the SCU  66 ,  86  a new count value is generated by retrieving the previous count value from memory and increasing the value by one (1) to obtain a new count value. When the SCU  66 ,  86  receives a shift signal it compares received count value to the previously received count value stored in the SCU memory  72 ,  92  for that signal type (ex: upshift, downshift) and device type (right shifter, left shifter). If the count value, signal type, and device type match the values stored in memory, the command is ignored as it is a duplicate signal that has already been processed. If the count value is different than the value stored in memory, the SCU  66 ,  86  will calculate a value “pending” by subtracting the count value in memory from the received count value. If the operator pushes the upshift lever once and no wireless transmissions were lost, the SCU  66  calculates a value of pending=1 and executes a command to the motor unit  64  to upshift once. Then the SCU  66  will record the new count value to memory for that signal type and device type. However, if the operator is rapidly pressing the upshift lever  38  and the system  22  is in a noisy wireless environment where wireless signals fail often, the SCU  66  may calculate a pending value greater than one. In this case a shift signal was lost, or the operator pressed the lever  38  more than once before the SCU  66  turned its transmitter and receiver on. If the SCU  66  receives a shift signal corresponding to an upshift input signal and calculates a pending value of 3, it is known that the upshift lever  38  had been operated three (3) times since the last shift signal corresponding to an upshift input signal was received, and will send a command to the motor unit  64  to upshift three (3) times. Then the SCU  66  will record the new count value to memory for that signal type and device type. The SCU  66  will also ignore signals corresponding to upshift or downshift input signals when the gear changer  30  is at the limit of its range. For this to occur, the SCU  66  will keep track of its position. 
     Other Shift Methods 
     The MCU  44  can also generate control signals regarding the state of the shift buttons  38  (upshift &amp; downshift). For example, when an upshift button  38  of unit  24   a  is pressed, the MCU transmits an “upshift button pressed” signal and when the upshift button is released, transmits an “upshift button released” signal. This feature is useful in a system  22  where there is no dedicated front gear changer shift button  42  on the shift units and the front gear changer  28  is toggle shifted by pressing the upshift and downshift buttons  38  of both units  24   a ,  24   b  together. In the case of a front shift, the SCUs  66 ,  86  will first receive both an upshift &amp; downshift button-pressed signal before receiving an upshift or downshift button-released signal, indicating that both buttons were pressed before either is released. When the SCU  86  of front gear changer  28  receives this signal sequence it will perform a front gear changer toggle shift. When the rear gear changer  30  receives this signal sequence, it will ignore them. 
     If the rear gear changer SCU  66  receives an upshift or downshift button-released signal without first receiving an upshift or downshift button-pressed signal, it can infer that the button-closed signal was lost or not transmitted from the MCU  44  because the button  38  was rapidly pressed and released. In this case the rear gear changer SCU  66  will go ahead and perform the upshift or downshift. 
     Although transmitted signals have only been described from the MCU  44 , the SCU  86 ,  66  in the front gear changer  28 , and rear gear changer  30  may also send signals to other devices. For example, the rear gear changer  30  can send a message to the front gear changer  28  indicating the current gear position of the rear gear changer. This would allow the front gear changer  28  to optimize the trim position of the front gear changer based on the position of the rear gear changer  30 . Other types of data the SCU  66 ,  86  of a device could transmit include battery level, number of shifts, device ID, temperature, error codes, firmware version, etc. 
     ANT/BTLE Bridge 
     It is also possible for the present system  22  to communicate with other third party devices using standard protocols such as ANT or Bluetooth Smart (BTLE). One of the devices in the system can collect data from the other devices such as battery level, gear position, firmware version, etc. and share the data with a third party device using a different communication protocol, effectively operating as an information bridge. 
     While this invention has been described by reference to particular embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiment, but that it have the full scope permitted by the language of the following claims.