Taximeter with tariff display mode controlled by removable memory addressable by fare rate keys
BACKGROUND OF THE INVENTION 
     This invention relates to an electronic taximeter, and more particularly to an electronic taximeter which provides simple changes in tariff display conditions in various operating modes (as determined by an actuated tariff key and a prior actuated tariff key). 
     Tariff display conditions in an electronic taximeter are generally fixed with regard to various operating modes of the taximeter. For instance, &#34;PAID&#34; is displayed upon actuation of a paid key, &#34;20% UP&#34; upon actuation of a 20% up key and &#34;OCCUPIED&#34; upon actuation of an occupied key. There may be a need to change these tariff display conditions in the respective operating modes of the taximeter due to tariff system reforms. In this case, a problem persists with the prior art taximeter in that the circuit arrangement thereof must itself be reconstructed whenever such changes are necessary. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a new and useful taximeter which avoids the above discussed problem with the prior art device. 
     It is another object of the present invention to provide a taximeter which allows simple changes in tariff display conditions in various operating modes without any change or modification in circuit construction. In other words, a taximeter according to the present invention is capable of optionally setting tariff display conditions in various operating modes without reconstructing the circuit arrangement within the taximeter body. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and many of the attendant advantages of the present invention will be readily appreciated as the same become better understood by reference to the following detailed description when, considered in conjunction with the accompanying drawings in which like reference numbers designate like parts throughout the figures thereof, and wherein: 
     FIG. 1 is a perspective view of the appearance of an embodiment of the present invention; 
     FIG. 2 is a schematic block diagram of an essential part of a circuit arrangement of the embodiment shown in FIG. 2; 
     FIG. 3 is a table indicating the relationship between address and information with regard to a memory removably fitted to the body of the taximeter shown and containing a succession of tariff display enabling and disabling signals; and 
     FIG. 4 is a schematic block diagram of address and cumulative value display sections. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the accompanying drawings, there is shown a taximeter constructed in accordance with an embodiment of the present invention. In FIG. 1, there are provided a given number of tariff keys TK, a tariff display L, a fare display DSP 1 , a cumulative value display DSP 2  and an extra fare display DSP 3 . The cumulative value display DSP 2  may be adapted to provide a display of total traveled distance, service traveled distance, number of runs, number of additional runs, accumulated fare due, extra fare, etc. 
     In FIG. 2, the tariff keys TK include an occupied key TK 1 , a 20% up key TK 2 , a wait/paid key TK 3 , a vacant key TK 4  and a system 3 key TK 5 . There are further provided preset keys SS including a tariff system preset key SS 4 . Depending on whether the preset key SS 4  is in the ON or OFF state, the taximeter shown herein is set in the distance meter system or combined time and distance meter system. When in the distance meter mode, the key TK 3  serves as a wait key, visually identified by a symbol reading &#34;WAIT&#34;. On the other hand, while in the combined time and distance meter system, the key TK 3  behaves as a paid key with an attendant display of &#34;PAID&#34;. 
     The remaining preset keys SS 1 , SS 2  and SS 3  are switches that determine which of three fare rate modes system 3 falls into &#34;30% UP&#34;, &#34;INCREASED BASIS FARE&#34; or &#34;VACANT OR FREE FOR HIRE&#34; mode. If SS 1  is turned ON and the rest remains OFF, then system 3 is set in the &#34;30% UP&#34; mode so that the system 3 key TK 5  serves as a 30% up key. If SS 2  is turned ON and other keys remain OFF, then system 3 falls into the &#34;INCREASED BASIS FARE&#34; mode. That is, in this case, the system 3 key TK 5  serves as an increased basis fare key. When SS 3  is in the ON state and the remaining switches are in the OFF state, system 3 belongs to the &#34;VACANT OR FREE FOR HIRE&#34; mode so that the system 3 key TK 5  functions as a vacant or free for hire key. 
     The definition of the key TK 5  is visually displayed based upon the operating mode as set up by the preset keys SS 1  -SS 3  (for instance, a key legend &#34;30% UP&#34; is displayed when the system 3 key serves as the 30% up key) in the same manner as upon actuation of the preset key SS 1 . 
     The above mentioned tariff display L includes a series of tariff lamps L 1  . . . L 5  each corresponding to the respective tariff keys TK 1  . . . TK 5 . When TK 3  serves as the wait key, a front plate is illuminated with the tariff lamp L 3  to read &#34;WAIT&#34;. When TK 3  serves as the paid key, the plate in front of the tariff lamp L 3  provides a visual display of &#34;PAID&#34;. Likewise, when TK 5  is the 30% up key, the tariff lamp L 5  displays &#34;30% UP&#34;. When TK 5  is the increased basis fare key, the tariff lamp L 5  displays &#34;INCREASED BASIS FARE&#34;. When TK 5  services as the vacant or free for hire key, the lamp L 5  provides &#34;VACANT OR FREE FOR HIRE&#34;. 
     FIG. 1 demonstrates the situation where the taximeter is placed in the combined time and distance meter system and system 3 is preset at the &#34;30% UP&#34; mode. 
     FIG. 2 shows a taximeter body TM including a distance counter CO 1 , a fare counter CO 2 , a revolution sensor CS, and the above discussed display DSP consisting of the fare display DSP 1 , the cumulative value display DSP 2  and the extra fare display DSP 3 . These components are well known in the art of taximeters with detailed disclosures thereof omitted herein. 
     The heart of the present invention will now be discussed in greater detail. A memory MU which contains a succession of tariff lamp enabling and disabling signals is fitted removably to the taximeter body. The detachable memory may be made up by a recently developed P-ROM, mask ROM or other components. The operation state of the respective tariff lamps L 1  . . . L 5  upon actuation of the tariff keys TK is determined by information contained in the memory MU. As is well known in the art, the memory MU has an address counter AR and an address decoder AD. An encoder EN provides coded signals as address codes for the memory MU, depending on a particular actuated tariff key, the preset conditions by the preset switches and a prior tariff key acutuated just before actuation of that particular tariff key. An actuated key detector KJ develops its output only when any tariff key TK is actuated. Latches LU 1 , LU 2 , LU 5  and LU 3  hold and store information fetched from a particular address area of the memory MU as specified by the address codes from the encoder EN. Another latch LU 4  holds an output resulting from actuation of the vacant key TK 4 . Being supplied with the output from the actuated key detector KJ, the latches LU (LU 1  . . . LU 5 ) accept and hold their input signals. Lamp drive circuitry DR (DR 1  . . . DR 5 ) enables or disables the tariff lamps L 1  . . . L 5  in response to the outputs of the latches LU (LU 1  . . . LU 5 ). 
     The taximeter will operate in the following manner as is better understood by reference to FIG. 3. TABLE 1 shows the relationship between the preset modes by actuations of the tariff keys TK and their corresponding addresses of the memory MU. 
     
                                           TABLE 1                                 
__________________________________________________________________________
                   (2)     (3)                                            
           (1)     PRESET  PRIOR                                          
           ACTUATED                                                       
                   CONDITION                                              
                           ACTUATED                                       
                                   MEMORY MU                              
MODE       TARIFF KEY                                                     
                   BY SWITCH                                              
                           TARIFF KEY                                     
                                   ADDRESS                                
__________________________________________________________________________
VACANT     vacant key              A.sub.0                                
OCCUPIED   occupied key            A.sub.1                                
(SYSTEM 1)                                                                
20% UP     20% up key              A.sub.2                                
(SYSTEM 2)                                                                
30% UP             SS1:ON                                                 
(SYSTEM 3) system 3 key                                                   
                   SS2:OFF         A.sub.3                                
                   SS3:OFF                                                
INCREASED          SS1:OFF                                                
BASIS FARE &#34;       SS2:ON          A.sub.4                                
(SYSTEM 3)         SS3:OFF                                                
VACANT             SS1:OFF                                                
(SYSTEM 3) &#34;       SS2:OFF         A.sub.5                                
                   SS3:ON                                                 
OCCUPIED/PAID                                                             
           wait/paid key                                                  
                   SS4:OFF occupied key                                   
                                   A.sub.6                                
20% UP/PAID                                                               
           &#34;         &#34;     20% up key                                     
                                   A.sub.7                                
                   SS1:ON                                                 
30% UP/PAID                                                               
           &#34;       SS2:OFF system 3 key                                   
                                   A.sub.8                                
                   SS3:OFF                                                
                   SS4:OFF                                                
                   SS1:OFF                                                
INCREASED  &#34;       SS2:ON  &#34;       A.sub.9                                
BASIS FARE         SS3:OFF                                                
/PAID              SS4:OFF                                                
                   SS1:OFF                                                
VACANT/PAID                                                               
           &#34;       SS2:OFF &#34;       .sup. A.sub.10                         
                   SS3:ON                                                 
                   SS4:OFF                                                
OCCUPIED/WAIT                                                             
           &#34;       SS4:ON  occupied key                                   
                                   .sup. A.sub.11                         
20% UP/WAIT                                                               
           &#34;         &#34;     20% up key                                     
                                   .sup. A.sub.12                         
                   SS1:ON                                                 
30% UP/WAIT                                                               
           &#34;       SS2:OFF system 3 key                                   
                                   .sup. A.sub.13                         
                   SS3:OFF                                                
                   SS4:ON                                                 
                   SS1:OFF                                                
INCREASED  &#34;       SS2:ON  &#34;       .sup. A.sub.14                         
BASIS FARE         SS3:OFF                                                
/PAID              SS4:ON                                                 
__________________________________________________________________________
 
    
     In TABLE 1, &#34;VACANT&#34; means the vacant or free for hire mode. TABLE 2 depicts the relationship between respective bits (t 4  . . . t 1 ) and the respective tariff lamps. 
     
                       TABLE 2                                                     
______________________________________                                    
BIT               TARIFF LAMP                                             
______________________________________                                    
t.sub.4           L.sub.1 (occupied)                                      
t.sub.3           L.sub.2 (20% up)                                        
t.sub.2           L.sub.3 (system 3)                                      
t.sub.1           L.sub.3 (wait/paid)                                     
______________________________________                                    
 
    
     It is assumed that each of the tariff lamps is enabled with information &#34;1&#34;  and disabled with information &#34;O&#34;. The following example will give a better understanding of the taximeter according to the present invention. When the vacant key TK 4  is actuated to set up the vacant mode, the tarifff lamp L 4  is enabled to display &#34;VACANT&#34;. In this case, the detector KJ senses that the vacant key TK 4  has been actuated and develops its output advising the latch LU 4  of that fact. As is clear from TABLE 1, all of the latches LU 1 , LU 2 , LU 5  and LU 3  are supplied with &#34;0&#34;. As a result, the only latch in the set state is the latch LU 4  which in turn enables the tariff lamp L 4  through the lamp drive circuit DR 4 , thus providing a visual display of &#34;VACANT&#34;. 
     In the case where the shown taximeter operates as the distance meter with system 3 falling into the increased basis fare mode, there is sometimes the need to set the wait mode in service (this is accomplished by actuating the wait key TK 3 ). At this time, the actuated key detector KJ produces its output signal, allowing the memory MU to deliver &#34;0011&#34; therefrom. The latches LU 5  and LU 3  are brought into the set state to enable the tariff lamps L 5  and L 3  whereas the other latches remain in the reset state. This indicates that the passanger vehicle is in the increased basis fare mode and also in the wait mode. 
     As note earlier, the taximeter embodying the present invention is given a greatest allowance in changes in the tariff displaying conditions because the enabling and diabling conditions of the tariff lamps in the respective operating modes are dependent and selectable by the information contained in the memory easily removable from the taximeter body. When the changing of the tariff display condtions becomes necessary, all that is needed is to replace the old memory MU with a new one (designed to accommodate to a new tariff rate regulation) or rewrite the contents of the memory MU via a simple measure. While, for example, the information shown in FIG. 3 is used in displaying the increased basis fare/wait modes by energizing both the increased basis fee tariff lamp and the wait tariff lamp, there is sometimes no requirement for indications of the two modes but a sole indication of the &#34;WAIT&#34; mode is enough even during the increased basis fare and wait modes. In this case, a new ROM (read only memory) which stores &#34;0001&#34; in the address A 14  may be available in place of the ROM illustrated in FIG. 3. In any case, a required change is attained not by reconstruction of the taximeter circuit but by easy exchange of the memory unit MU. 
     FIG. 4 shows details of the cumulative value display DSP 2 . As stated above, the cumulative value display can provide varied sorts of cumulative values calculated from the taximeter body, for example, total traveled distance, service traveled distance, number of service runs, number of additional runs, accumulated fare due, extra number, etc. The kind of these cumulative values may be identified by provision of an address display as follows: 
     
                       TABLE 3                                                     
______________________________________                                    
ADDRESS                                                                   
DISPLAY         CUMULATIVE DATA                                           
______________________________________                                    
0               total traveled distance                                   
1               service traveled distance                                 
2               number of service runs                                    
3               number of additional runs                                 
4               accumulated fare                                          
5               extra number                                              
______________________________________                                    
 
    
     The cumulative value display DSP 2  is made of a five digit cathode common LEDs (light emitting diodes) with the extreme left digit serving as an address display 41 and the remaining four digits as the main (cumulative value) display 42. Count circuitry 4 comprises a four digit, six channel accumulator counter (counting respective channel inputs DI 0  . . . DI 5 ), an address counter incremented progressively in the order of 0→1→2→3→4→5→0→1 upon each actuation of an address up switch (preferably, mounted on the front panel of the taximeter) and a digit timing counter developing time-sharing digit selection signals T 1  . . . T 5 . Changeovers take place in the count circuitry 7 to select sequentially one of channels leading to its output line each time the address up switch is depressed. The contents of the address counter storing the contents of the selected channel and the cumulative data with respect to that selected channel are fetched in succession in synchronism with the time-sharing signals T 1  . . . T 5 . BCD codes from the count circuitry 7 are converted via a decoder driver 8 into anode segment selection signals compatible with the cumulative value display DSP 2 . A second driver 9  develops cathode common selection signals based upon the time-sharing signals T 1  . . . T 5 . 
     An additional driver 10 which enables a decimal point LED 11 by supplying its output to tha cathode of the decimal point LED 11 is necessary for the practice of displaying the address and cumulative data. The cathode of the decimal point LED is common to the counterpart of the address display 41. The cumulative data display DSP 2  is driven on the time sharing basis and the decimal point LED 11 is enabled in timed relationship with the address display 41. 
     It is well known that the relationship between the number of revolutions of a transmission system and traveled distance differs from vehicle to vehicle due to the gear ratio of the transmission, the air pressure of tires, the diameter of tires, etc. For this reason the compensation by a so-called vehicle constant is necessary to accommodate measured distances displayed by the taximeter and actual traveled distances within a permitted range by regurations. When the compensation constant K is calculated using the shown taximeter, the vehicle is run by a predetermined distance (for example, b&#39;=500 m) and the readout of the cumulative value display DSP 2  is then used for calculation of the vehicle constant K. Since the number n of pulses on the display DSP 2  and the number N of reference pulses per 1 Km, the vehicle constant K can be calculated from the following equation: 
     
         K=b&#39;N/n 
    
     In view of the foregoing requirement, it is favorable that the cumulative counter be provided with a conventional zeroing device. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such modifications are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications are intended to be included within the scope of the following claims.