[ 0014 ] fig1 is a side view of a particular embodiment of a bicycle 1 . bicycle 1 comprises a frame body 2 constructed by welding together tubing having noncircular cross - sections . a front fork 3 is mounted to the front of frame body 2 for rotation around an inclined axis , and a handlebar assembly 4 is mounted to the top of front fork 3 . a saddle 18 is mounted to the upper middle part of frame body 2 , a drive mechanism 5 is mounted to the lower part of frame body 2 , a front wheel 6 is rotatably mounted to the bottom of front fork 3 , and a rear wheel 7 having a hub dynamo 10 is rotatably mounted to the rear of frame body 2 . hub dynamo 10 houses an alternating current generator 19 ( fig3 ) for generating electricity through rotation of rear wheel 7 . a front transmission 8 including a front derailleur 26 f is mounted to the lower middle part of frame body 2 , and a rear transmission 9 including a rear derailleur 26 r is mounted to the rear of frame body 2 . a front suspension 13 f is mounted to front fork 3 , and a rear suspension 13 r is mounted between stationary and articulated portions of frame body 2 . as shown in fig2 handlebar assembly 4 comprises a handle stem 12 mounted to the top of front fork 3 and a handlebar 15 mounted to the top of handle stem 12 . brake lever assemblies 16 and grips 17 are mounted at the opposite ends of handlebar 15 . the right side brake lever assembly 16 includes a rear downshift switch 20 a for manually downshifting rear derailleur 26 r in single increments , a rear upshift switch 20 b for manually upshifting rear derailleur 26 r in single increments , and a mode switch 21 a for switching between automatic and manual shift modes . the left side brake lever assembly 16 includes a front downshift switch 20 c for manually downshifting front derailleur 26 f in single increments , a front upshift switch 20 d for manually upshifting front derailleur 26 f in single increments , and a suspension control switch 21 b for adjusting the stiffness of front suspension 13 f and rear suspension 13 r . as shown in fig1 drive mechanism 5 comprises a crank 27 rotatably mounted at the bottom bracket of frame body 2 , front and rear transmissions 8 and 9 , and a chain 29 . front transmission 8 comprises , for example , three front sprockets f 1 - f 3 and front derailleur 26 f . front sprockets f 1 - f 3 are mounted to crank 27 , and front derailleur 26 f is mounted on frame body 2 . rear transmission 9 comprises , for example , a multiple sprocket assembly 25 having eight rear sprockets r 1 - r 8 and rear derailleur 26 r . multiple sprocket assembly 25 is mounted to rear wheel 7 and rear derailleur 26 r is mounted at the back of frame body 2 . crank 27 comprises a right crank arm 27 a and a left crank arm 27 b , wherein front sprockets f 1 - f 3 are mounted to right crank arm 27 a . chain 29 engages one of the front sprockets f 1 - f 3 and one of the rear sprockets r 1 - r 8 . front sprockets f 1 - f 3 are arranged in the order of an increasing number of teeth , wherein front sprocket fl is the laterally innermost front sprocket having the least number of teeth , and front sprocket f 3 is the laterally outermost front sprocket having the most number of teeth . rear sprockets rl - r 8 are arranged in the order of a decreasing number of teeth , wherein rear sprocket r 1 is the laterally innermost rear sprocket having the most number of teeth , and rear sprocket r 8 is the laterally outermost rear sprocket having the least number of teeth . a rotation sensor ( not shown in fig1 ) is provided for sensing the rotation of crank 27 . the presence or absence of rotation of crank 27 ordinarily is used in part to control the operation of front and rear transmissions 8 and 9 . for example , derailleurs cannot shift properly when crank 27 is stationary , so any requested operation of a derailleur may be delayed until crank 27 is rotating . a rotation sensor typically comprises a reed switch 23 ( fig3 ) mounted to frame body 2 and a magnet ( not shown ) mounted to one of the crank arms 27 a and 27 b so that reed switch 23 provides a pulse whenever the magnet passes by . a controller 11 ( fig3 ) is provided for controlling various components including the front and rear transmissions 8 and 9 and the front and rear suspensions 13 f and 13 r . more specifically , controller 11 controls front and rear transmissions 8 and 9 in response to the operation of shift switches 20 a - 20 d and mode switch 21 a , and it controls front and rear suspensions 13 f and 13 r in response to the operation of control switch 21 b . controller 11 also automatically controls the operation of front and rear transmissions 8 and 9 in response to bicycle velocity . as shown in fig3 and 4 , controller 11 comprises a first control unit 30 , a second control unit 31 , and a third control unit 32 . first control unit 30 may be mounted , for example , on the bottom bracket of frame body 2 in proximity to the rotation sensor and front derailleur 26 f , and it is connected to alternating current generator 19 . the electrical current generated by alternating current generator 19 powers first control unit 30 , and first control unit 30 uses the supplied electrical current to control the operation of front derailleur 26 f , rear derailleur 26 r and rear suspension 13 r . first control unit 30 also supplies control signals ( e . g ., a velocity signal ) superimposed on a relatively low current signal ( e . g ., pulse code modulated ( pcm ) signals ) to second control unit 31 and third control unit 32 . since first control unit 30 is disposed on the bottom bracket of frame body 2 , it is fairly close to alternating current generator 19 . as a result , a short power cable may be used to connect first control unit 30 to alternating current generator 19 , and the communication of power between the two may be carried out with high efficiency . first control unit 30 controls front transmission 8 , rear transmission 9 and rear suspension 13 r in accordance with the operating mode set by mode switch 21 a . in this embodiment , in automatic mode , front transmission 8 and rear transmission 9 are controlled according to bicycle velocity , and rear suspension 13 r may be set in one of two levels ( e . g ., hard or soft ) depending on bicycle velocity . in manual mode , rear transmission 9 is controlled by the operation of shift switches 20 a and 20 b , front transmission 8 is controlled by the operation of shift switches 20 c and 20 d , and rear suspension 13 r is controlled by the operation of control switch 21 b . first control unit 30 has a first control portion 35 that comprises a computing component in the form of a microcomputer including a cpu , memory , i / o interface , and the like . a number of modules are connected to first control portion 35 . such modules include a waveform shaping circuit 36 for generating a velocity signal from pulses output from alternating current generator 19 ; a charging control circuit 33 ; a first power storage element 38 a ; a second power storage element 38 b ; the rotation sensor reed switch 23 ; a power supply and communications circuit 34 that switches on and off a relatively low current signal from second power storage element 38 b to second control unit 31 and third control unit 32 and provides the composite power / control pcm signals mentioned above to second control unit 31 and third control unit 32 ; a power on / off switch 28 that switches on and off a relatively high current signal from first power storage element 38 a to second control unit 31 ; a front motor driver ( fmd ) 39 f for operating a front derailleur motor ( fdm ) 44 f for front derailleur 26 f ; a rear motor driver ( rmd ) 39 r for operating a rear derailleur motor ( rdm ) 44 r for rear derailleur 26 r ; a front operating location sensor ( fls ) 41 f for front derailleur 26 f ; a rear operating location sensor ( rls ) 41 r for rear derailleur 26 r ; a rear suspension driver ( rsd ) 43 r for operating rear suspension 13 r ; and a first memory component 47 for storing travel information such as total distance ( in which case it functions as a cumulative information memory ) and so on . first memory component 47 may comprise a nonvolatile memory such as an eeprom for retaining the data stored therein even when the power source is interrupted . second control unit 31 controls front suspension 13 f in response to control signals sent by first control unit 30 . more specifically , in automatic mode the hardness of front suspension 13 f is adjusted depending on bicycle velocity , whereas in manual mode the hardness of front suspension 13 f is adjusted in response to the operation of control switch 21 b . second control unit 31 also provides control information from switches 20 a - 20 d , 21 a and 21 b to first control unit 30 . for these functions , second control unit 31 includes a third power storage element 38 c , a front suspension driver ( fsd ) 43 f for operating front suspension 13 f , a second control portion 45 such as a computing component in the form of a microcomputer , a first receiver circuit 46 for receiving composite power / control signals from power supply and communications circuit 34 in first control unit 30 , and a buffer 48 . as shown in fig2 second control unit 31 is attached to handlebar 15 of handlebar assembly 4 by means of a bracket 50 , with the components of second control unit 31 housed within bracket 50 . third control unit 32 is housed in a case member 54 detachably installed on second bracket 50 , and it functions primarily as a display component . third control unit 32 has a liquid crystal display ( lcd ) 56 that displays travel information such as bicycle velocity , cadence , distance traveled , shift position , suspension status , and other information . third control unit 32 controls lcd 56 in response to control signals output by first control unit 30 . for that purpose , third control unit 32 also includes a fourth power storage element 38 d , a third control portion 55 such as a computing component in the form of a microcomputer , a voltage stabilizing circuit 57 , a backlight 58 for illuminating display 56 , a second memory component 59 , and a second receiver circuit 61 for receiving composite power / control signals from power supply and communications circuit 34 in first control unit 30 . a mode switch 24 protrudes outward from case member 54 as shown in fig2 and provides signals to third control portion 55 to select the types of information displayed on lcd 56 ( in which case mode switch 24 functions as a display switching component ). mode switch 24 also may be used to reset travel distance ( i . e ., begin calculating travel distance anew ) such as by depressing mode switch 24 for a selected time interval ( e . g ., 3 seconds or longer ), and to perform other control functions . second memory component 59 may store travel information such as travel distance , total distance ( in such cases it functions as a cumulative information memory ), travel time , and so on . in this embodiment , second memory component 59 comprises a nonvolatile memory such as an eeprom so that the various types of data may be retained even when the power source is interrupted as a result of third control unit 32 being detached from second control unit 31 . as shown in fig9 second memory component 59 may be divided into a total distance ( od ) memory area 59 a for storing total distance od output from first control portion 35 , a travel distance ( td ) memory area 59 b for storing travel distance td since reset , a reset total distance ( od 1 ) memory area 59 c for storing the total distance od at reset , a velocity ( v ) memory area 59 d for storing changes in the time of the velocity v to display average velocity , maximum velocity , or the like , and a data memory area 59 e for storing other data . returning again to first control unit 30 , second power storage element 38 b is connected to first power storage element 38 a through a diode 42 . diode 42 causes electrical current to flow in one direction only from first power storage element 38 a to second power storage element 38 b . in other words , diode 42 prevents reverse current flow from second power storage element 38 b to first power storage element 38 a . in this embodiment , first power storage element 38 a is employed mainly as a power supply for electrical components with high power consumption and high electrical capacity , such as drivers 39 f , 39 r , 43 f and 43 r , whereas second power storage element 38 b is employed as a power supply for electrical components having low power consumption and low electrical capacity , such as first control portion 35 , third control portion 55 , and lcd 56 . first and second power storage elements 38 a and 38 b may comprise high - capacity capacitors , such as electric double layer capacitors . these capacitors store direct current power output from alternating current generator 19 and rectified by charging control circuit 33 . of course , instead of capacitors , first and second power storage elements 38 a and 38 b could comprise secondary cells , such as nickel - cadmium , lithium ion , or nickel hydrogen cells . charging control circuit 33 comprises a rectifier circuit 37 and a charge on / off switch 40 . rectifier circuit 37 rectifies current output from alternating current generator 19 to produce dc current , and charge on / off switch 40 switches on and off the current output by the rectifier circuit 37 in response to control signals from first control portion 35 . more specifically , first control portion 35 monitors the voltage of first power storage element 38 a . below a predetermined voltage ( e . g ., 5 . 5v ), first control portion 35 outputs a control signal for switching on the charge on / off switch 40 , thus allowing first power storage element 38 a to charge . on the other hand , if the voltage of first power storage element 38 a goes above a predetermined voltage ( e . g ., 7 v ), first control portion 35 outputs a control signal for switching off the charge on / off switch 40 , thereby preventing excessive voltage from accumulating in first power storage element 38 a . power on / off switch 28 is connected to first power storage element 38 a and to first control portion 35 . power is switched on to activate second control portion 45 and fsd 43 f when it is necessary to adjust front suspension 13 f , but power is switched off otherwise . as a result , needless power consumption from first power storage element 38 a can be avoided . power supply and communications circuit 34 is connected to second storage element 38 b and to first control portion 35 . as noted above , power supply and communications circuit 34 switches on and off a relatively low current signal from second power storage element 38 b to second control unit 31 and third control unit 32 and provides composite power / control signals to second control unit 31 and third control unit 32 , thus functioning as an information output . it does this through a single communication line 52 to reduce components . power supply and communications circuit 34 is controlled in response to information such as velocity , distance traveled , current transmission gear , automatic vs . manual modes , suspension hardness and the like . as shown in fig4 first receiver circuit 46 in second control unit 31 is connected to power supply and communication circuit 34 through communication line 52 , thus functioning as an information input . first receiver circuit 46 extracts the control signals from the composite power / control signals from power supply and communication circuit 34 and communicates the control signals to second control portion 45 . third power storage element 38 c also is connected to power supply and communications circuit 34 . third power storage element 38 c may comprise , for example , a relatively high capacity capacitor such as an electrolytic capacitor , and it is provided to smooth the electrical current from the composite power / control signals received from power supply and communications circuit 34 . third power storage element 38 c provides operating power to buffer 48 that functions to stabilize the analog voltage signals from shift switches 20 a - 20 db and control switches 21 a and 21 b . second receiver circuit 61 and fourth power storage element 38 d in third control unit 32 also are connected to power supply and communication circuit 34 ( in parallel with first receiver circuit 46 ). second receiver circuit 61 extracts the control signals from the composite power / control signals from power supply and communication circuit 34 , thus functioning as an information input , and communicates the control signals to third control portion 55 . fourth power storage element 38 d may comprise an electrolytic capacitor that provides operating power directly to third control portion 55 and indirectly to backlight 58 through voltage stabilizing circuit 57 . voltage stabilizing circuit 57 stabilizes the voltage from fourth power storage element 38 d to avoid flickering of backlight 58 that otherwise may be caused by the pulsed control signals superimposed on the power signals from power supply and communications circuit 34 . [ 0032 ] fig5 illustrates an embodiment of information that may be shown on a display screen 71 of lcd 56 . in this embodiment , display screen 71 comprises a main number display portion 72 , an auxiliary number display portion 73 , a description display portion 74 , a rear gear position display portion 75 , and a front gear position display portion 76 . information such as bicycle velocity , time , etc . is displayed in numerical format in main number display portion 72 and auxiliary number display portion 73 . description display portion 74 displays a description of the contents of main number display portion 72 and auxiliary number display portion 73 , as well as showing the transmission operating mode . for example , “ vel ” indicates travel velocity , “ dst ” indicates distance traveled , “ clk ” indicates current time , “ tim ” indicates travel time , an “ gea ” indicates current shift position of the front and rear transmissions , “ at ” indicates automatic shift mode , “ mt ” indicates manual shift mode , and so on . the unit of velocity can be switched between “ km / h ” and “ mile / h ”, and the unit of distance can be switched between “ km ” and “ mile .” the rear gear position display portion 75 shows the gear position of the rear transmission 9 , and it comprises a plurality of ( e . g ., nine ) elliptical display symbols gradually decreasing in diameter from left to right to correspond with the size of the actual rear sprockets r 1 - r 8 . when initializing lcd 56 , the number of sprockets for rear transmission 9 can be set to match the actual number of sprockets installed on the bicycle . for example , when rear transmission 9 has eight sprockets , as in this embodiment , the number of rear sprockets is input to the cycle computer . thereafter , eight elliptical display symbols are displayed from left to right in rear gear position display portion 75 , with the one remaining symbol at the right end not displayed . similarly , the front gear position display portion 76 shows the gear position of the front transmission 8 , and it comprises a plurality of ( e . g ., three ) elliptical display symbols gradually increasing in diameter from left to right to correspond with the size of the actual front sprockets f 1 - f 3 . when initializing lcd 56 , the number of sprockets for front transmission 8 can be set to match the actual number of sprockets installed on the bicycle . for example , when front transmission 8 has two sprockets , the number of front sprockets is input to the cycle computer . thereafter , two elliptical display symbols are displayed from right to left in front gear position display portion 76 , with the one remaining symbol at the left end not displayed . as a result of this arrangement , the sprocket positions of front and rear transmissions 8 and 9 may be ascertained intuitively at a glance . in operation , the alternating current generator 19 of hub dynamo 10 generates electricity as the bicycle is pedaled , and this electricity is supplied to first control unit 30 , with power being stored by first and second power storage elements 38 a and 38 b . since alternating current generator 19 is disposed on rear wheel 7 , first and second power storage elements 38 a and 38 b can be charged simply by turning the pedals , with the bicycle remaining stationary , by lifting the rear wheel . thus , it is a simple matter to at least partially charge first and second power storage elements 38 a and 38 b by turning the pedals to allow setting up of the electronically operated transmissions and the information displayed on lcd 56 . in automatic shift mode , derailleurs 26 f and 26 r and suspensions 13 f and 13 r are controlled according to a velocity signal generated by first control portion 35 from the shaped pulse output by waveform shaping circuit 36 . more specifically , a shift operation is performed when the bicycle velocity is greater or less than predetermined values , wherein rear derailleur 26 r is given preference in ordinary shift operations . also , when velocity goes above a predetermined value , the hardness of the suspensions 13 f and 13 r is increased . meanwhile , first control portion 35 calculates total distance od from the shaped pulse output by waveform shaping circuit 36 and stores the result in first memory component 47 . total distance od may be calculated by counting the shaped pulses , dividing the sum by the number of pulses per wheel rotation , and multiplying the quotient by the wheel circumference . other cumulative information may be calculated as appropriate . control signals based on information such as velocity , distance , transmission gear , automatic vs . manual modes , suspension hardness , and the like , are generated by first control portion 35 and output to power supply communications circuit 34 . power supply and communications circuit 34 superimposes the control signals on a power signal derived from second power storage element 38 b to produce the appropriate pcm signals . the composite power / control signals are then communicated to second control portion 45 and third control portion 55 , whereupon the composite power / control signals are decoded . second control portion 45 is powered by power signals received from power on / off switch 28 and outputs to rsd 43 f signals for controlling front suspension 13 f in response to the control signal portion of the composite power / control signals received from power supply and communications circuit 34 . the power signal portion of the composite power / control signals received from power supply and communications circuit 34 powers buffer amp 48 . when a control switch 21 a or 21 b or a shift switch 20 a - 20 d is operated , a signal of different analog voltage is output to first control portion 35 via buffer amp 48 , and first control portion 35 generates the appropriate control signals for controlling one or more of derailleurs 26 f and 26 r or suspensions 13 f and 13 r , or for changing the transmission operating mode . third control portion 55 is powered by the power signal portion of the composite power / control signals received from power supply and communications circuit 34 . third control portion 55 performs distance calculations and the like based on the control signal portion of the composite power / control signals received from power supply and communications circuit 34 and thereafter outputs to lcd 56 velocity and other kinds of information . when driving a motor - driven electrical component having large electrical capacity , such as derailleurs 26 f and 26 r or suspensions 13 f and 13 r , there is a voltage drop in first power storage element 38 a . if first control portion 35 , third control portion 55 and lcd 56 were powered by first power storage element 38 a , the voltage drop could cause the microprocessors and other electronics to reset or cause some other problem . since the power for these components in this embodiment is provided from second power storage element 38 b connected to first power storage element 38 a through diode 42 , the components are unaffected by voltage drops in first power storage element 38 a . while second control portion 45 is powered by first power storage element 38 a , it is normally off except when needed to control front suspension 13 f . consequently , second control portion 45 is unaffected by voltage drops in first power storage element 38 a . more specific operations of first control unit 30 and third control unit 32 now will be described with reference to fig6 - 8 . fig6 is a flow chart of a particular embodiment of a main processing routine in first control unit 30 . when rear wheel 7 turns , alternating current generator 19 supplies electrical power to first control unit 30 , and this power is stored in first power storage element 38 a and second power storage element 38 b . the power stored in second power storage element 38 b is supplied to first control portion 35 , and initialization of first control portion 35 is carried out in step s 1 of fig6 . in this initialization process , the transmission operating mode may be set to automatic shift mode , for example . in step s 2 , a timer that measures the processing time per microcomputer processing cycle is started . in step s 3 , a data processing routine shown in fig7 is performed for computing total distance and the like . in step s 4 , a shift control process ( automatic or manual ) is executed in a manner described above . in step s 5 , another process such as the establishment of the operating mode is executed . in step s 6 , the process waits for the started timer to stop . when that occurs , the routine returns to step s 2 . [ 0042 ] fig7 is a flow chart of a particular embodiment of the data processing routine . it is first determined in step s 10 whether or not a pulse from the waveform shaping circuit 36 has been received . if so , a pulse count is incremented in step s 13 , total distance od is computed from the pulse count as described above in step s 14 , the computed total distance od is stored as the most recent total distance in first memory component 47 in step s 15 , velocity data v is computed from the pulses output by waveform shaping circuit 36 in step s 16 , and the computed velocity data v is stored in first memory component 47 in step s 17 . storing these values allows the most recent data to be output despite differences between computation timing and output timing . in any event , it is then determined in step s 11 whether or not shift position data sh from the operating position sensors 41 r and / or 41 f has been received . if so , the data is converted to shift position data sh for display and is stored in first memory component 47 in step s 18 . thereafter , the total distance od , velocity data v , shift position data sh and the like are output through communication line 52 to third control unit 32 for display . [ 0044 ] fig8 is a flow chart of a particular embodiment of a main processing routine in third control unit 32 . when power is supplied from second storage element 38 b through communication line 52 , third control portion 55 in third control unit 32 performs initialization in step s 20 . in this initialization process , the units for distance or velocity may be set , for example . in step s 21 , a timer that measures the processing time per microcomputer processing cycle of the third control portion 55 is started . in step s 22 , a display process is performed to display velocity , distance , front and rear shift positions , and other data as appropriate . in this embodiment , either travel distance td or total distance od is selected for display on the auxiliary number display portion 73 in response to the operation of mode switch 24 , thus allowing the display area to be more compact . it is then determined in step s 23 whether or not velocity v or total distance od data has been received from first control portion 35 through communication line 52 . if so , the received total distance od is stored in the total distance od memory area 59 a of second memory component 59 in step s 27 . then , in step s 28 , the reset total distance od 1 stored in the reset total distance od 1 memory area 59 c is subtracted from the stored total distance od to compute the travel distance td , and the travel distance is then stored in the travel distance td memory area 59 b of second memory component 59 . the total distance od or travel distance td is displayed at the next occurrence of the display process in step s 22 . in any event , it is determined in step s 24 whether or not mode switch 24 has been pressed for a long time ( thereby functioning as a start input component ). if so , the travel distance td stored in the travel distance td memory area 59 b is reset to 0 in step s 29 , and the current total distance od is stored as the reset total distance od 1 in the reset total distance od 1 memory area 59 c , in which case reset total distance od 1 functions as reference cumulative information and reset total distance od 1 memory area 59 c functions as a reference information memory . storing the reset total distance od 1 as reference cumulative information allows the travel distance td to be accurately calculated from a subsequently received total distance od even when the power source is interrupted , such as when third control unit 32 is detached from second control unit 31 . in any event , another process such as one triggered by a normal operation of mode switch 24 is executed in step s 25 . then , the process waits in step s 26 for the timer started in step s 21 to stop . when that occurs , the routine returns to step s 21 . it should be readily apparent that the total distance od is constantly computed by first control portion 35 of first control unit 30 , which tends to be more permanently mounted on the bicycle , and the computed total distance od is displayed on lcd 56 in third control unit 32 . in other words , the total distance od is not computed by third control unit 32 at the display end of the cycle computer , but is computed by first control unit 30 , which is separate from the display end . as such , the total distance od can be properly displayed even when third control unit 32 is replaced . furthermore , when a plurality of bicycles are owned , the total distances of each of the several bikes can be properly displayed with just one third control unit 32 . the total distance also can be properly displayed when third control unit 32 is mounted , regardless of whether or not it was temporarily detached . while the above is a description of various embodiments of inventive features , further modifications may be employed without departing from the spirit and scope of the present invention . for example , in the above embodiment , first control unit 30 computed the total distance , and the total distance was output to third control unit 32 . alternatively , total distance could be calculated by another component , such as second control unit 31 or some other control unit to which third control unit 32 could be attached . in the above embodiment , wheel rotation information was used to calculate velocity and distance , but such data also could be calculated from rotation information from the pulley of the rear derailleur 26 r or crank 27 . if so , wheel rotation information could be derived from this information plus shift position information . in the above embodiment , bicycle velocity was derived from signals produced by alternating current generator 19 , which obviates the need for a dedicated rotation information output component . the use of alternating current generator 19 in this manner also allows a plurality of signals to be obtained per revolution of the wheel which , in turn , produces a more precise computation of total distance . however , bicycle velocity could be derived from signals produced by conventional velocity sensors comprising a reed switch and one or more magnets that detect wheel rotation . in the above embodiment , the travel distance from a starting point was computed , but the remaining travel distance also may be computed and displayed when the travel distance is known in advance such as during training or touring . such cases may include a reference information input component ( such as mode switch 24 ) for inputting reference information such as a target travel distance ; and a remaining distance computation component ( such as third control portion 55 ) for computing the remaining travel distance by subtracting the computed travel distance from the input target travel distance . for example , a step for inputting the target travel distance can be inserted after the display process in step s 22 , the travel distance td can be computed in step s 28 for each signal received in step s 23 , and the computed travel distance td then can be subtracted from the input target travel distance to compute the remaining travel distance . the remaining travel distance or the target travel distance also may be reset in step s 29 in the same manner as for the travel distance td . in the above embodiment , first control unit 30 , second control unit 31 and third control unit 32 were operatively coupled by wiring them together , but any of them may be operatively coupled by a wireless communication arrangement . the size , shape , location or orientation of the various components may be changed as desired . components that are shown directly connected or contacting each other may have intermediate structures disposed between them . the functions of one element may be performed by two , and vice versa . the structures and functions of one embodiment may be adopted in another embodiment . it is not necessary for all advantages to be present in a particular embodiment at the same time . every feature that is unique from the prior art , alone or in combination with other features , also should be considered a separate description of further inventions by the applicant , including the structural and / or functional concepts embodied by such feature ( s ). thus , the scope of the invention should not be limited by the specific structures disclosed or the apparent initial focus or emphasis on a particular structure or feature .