WO1980002207A1

WO1980002207A1 - Electronic taximeter

Info

Publication number: WO1980002207A1
Application number: PCT/AU1980/000003
Authority: WO
Inventors: G Schmidt
Original assignee: G Schmidt
Priority date: 1979-04-11
Filing date: 1980-04-11
Publication date: 1980-10-16
Also published as: EP0026778A4; EP0026778A1; JPS56500511A

Abstract

An electronic taximeter having a microcomputor (30) is adapted to store the current calibration factor of the meter and cause, upon initiation, display thereof on an electronic display (54). An electronic revolution counter (47) is adapted to progressively count and display the revolutions of a speedometer cable input to said meter such that calibration may be checked by driving the vehicle over a measured distance. Calibration may be readily altered merely by selecting different combinations of an 8-switch dual-in-line package (44). Other features include a real time digital clock (31) whereby total engaged time of the taxi during any particular period and the time of commencement and conclusion of a particular fare may be computed. Tariff rates may be altered by replacement of a single re-programmable and hence re-usable memory chip (33) and a miniature rechargeable battery (35) continuously trickle charge by the vehicle electrical supply ensures retention of all data including current operation mode data for up to about six months in the event of loss or failure of said supply. This latter feature is made possible by cyclically dumping, about every millisecond, current operation mode data into low power read/write memory circuits, wherein all other data is also stored, and powering said memory circuit by said battery in the event of said loss or failure.

Description

TITLE: ELECTRONIC TAXIMETER

. The present invention relates to an electronic meter and in particular to an electronic taximeter.

Electronic taximeters utilizing either analogue or digital circuitry are known and overcome a number of the inherent disadvantages of electromechanical taximeters. However, the known electronic meters also have a number of disadvantages which make them less attractive in use than they might otherwise be.

For example, every taximeter must be calibrated to suit the individual vehicle in order to meet accuracy tolerances required by regulatory bodies and such calibration must be made regularly in view of variation in certain parameters such as tyre diameter. Thus in order to meet the accuracy required such calibration is made upon installation of the meter and at every rate change and usually involves measurement of the revolutions of the speedometer cable (which provides input to the meter) over a measured distance travelled (say one kilometer) . In order to carry out the calibration it is firstly necessary with known meters to disconnect the said cable from the meter and attach thereto a revolution counter. The vehicle is then driven over a known distance and calibration is done. Any adjustment required is effected by either a gear-ratio change, patchfield link change on printed circuit board or trim of a potentiometer. Any of these adjustments is either time consuming or clumsy and can involve component cost.

Furthermore, in known electronic taximeters, tariff rate changing procedures for such variables as distance travelled, elapsed time, initial fare or flagfall fare (increment value) and extras (increment value) are relatively costly to implement considering they occur a significant number of times overthe life of a meter. In the case of most electronic taximeters the procedure involves either changing small circuit boards, replacing components, trimming potentiometers or a combination there These time consuming procedures generally require the mete to be out of the vehicle for at least one hour. In one electronic taximeter currently available, only a single memory chip requires replacement but _.although this reduces labour costs, the cost of the chip, together with labour cost, makes the total expense involved about the same as that incurred with any of the aforementioned procedures. A still further disadvantage with known electronic meters is the manner in which they store vital operating information describing the work done and operating efficiency of the taxi. Many electronic meters still use electromechanical counters for this purpose and these are noisy in operation, bulky in size, and prone to wear. One taximeter is known where these counters have been replaced by microcomputer memory, which requires energization at all times to ensure that data is maintained intact. To ensure against loss of said data duringdisconnection of the meter from the vehicle battery, a small dry cell is incorporated into said meter to temporarily supply the memory in the event of said disconnection. Such batteries however, are only guaranteed to maintain supply for 37 hours which is considered to be most inadequate by most taxi owners and there are also reliability problems.

Associated with the aforementioned disadvantages i known meters, is the further disadvantage that known electronic meters will lose the value of the fare indicate if supply failure or disconnection occurs during meter operation. This situation occurs from time to time and causes anxiety in taxi drivers, who are permitted to

OMPI charge passengers only what is indicated on the meter.

It should be further noted that conventional meters have provision for recording total distance travelled as well as paid distance travelled and the ratio of these two parameters provides a measure of driver efficiency.

However, this measure of driver efficiency does not take account of the time the taxi may remain stationary waiting for a fare and consequently the measurement is deficient in this regard. Furthermore, many charge account customers require the driver to fill out a coupon at the end of a fare indicating the time the fare commenced and ended, as well as the total distance travelled and often the driver overlooks to record this information upon commence¬ ment of the fare and consequently has to make a guess at the end of the fare. This is a further deficiency of known meters.

Thus it is an object of this invention to provide an improved taximeter which avoids one or more of the aforementioned disadvantages and provides further .features and advantages as will become apparent herein below.

Accordingly one broad form of the invention provides an electronic taximeter including a microcomputer memory therein, said memory being arranged to store and provide on initiation a read-out to an electronic display of the current calibration factor for which the meter is calibrated, said meter further including an electronic revolution counter adapted to operate in conjunction with said display to provide a count and read-out of the revolutions of the speedometer cable providing input data to said meter, whereby calibration of the meter may be checked by driving the vehicle over a measured distance.

In order that the invention may be more readily understood a particular embodiment relating to a taximeter will now be described with reference to the accompanying drawings wherein;

Fig. 1(a) is one part of a circuit block diagram of a taximeter according to the embodi¬ ment, Fig. 1(b) is the other part of the diagram of

Fig. 1(a) and Fig. 2 is a program flow chart for the taximeter shown in Figs. 1(a) and 1(b) . Reference is initially made to Fig. 1(a) . Circuit

30 comprises the central element of the taximeter's electronic system. It is a microcomputer circuit comprisi a "central processing unit" which performs all the calculations required and interprets the program instruc- tions; a "hardware timer" which is controlled and monitore by the "central processing unit" to count out accurate time intervals; some "read/write memory" which is used lik a scratchpad to store intermediary calculation results, and to store "flags" and parameters describing the meter's current operation mode; and "input-output" interface circuits through which the "central processing unit" may monitor and control other electronic activities in the system, such as the keypad and displays.

Circuit 30 may be implemented by a number of discrete circuit packages, the number depending on the level of "integration" or sophistication chosen for each circuit component required to implement the complete circuit. For reasons of size reduction and assembly time minimization a single "large-scale-integrated circuit" has to be used to implement the complete circuit block 30.

Circuit 31 is frequency reference which provides the basic timing source required to operate the complete taximeter system. It is directly connected to circuit 30 since the latter is the central electronic element via which all other circuitry is controlled. Circuit 31 may be an oscillating L-C circuit, other similar discrete oscillator or a single quartz crystal. The latter has been chosen because crystals may be manufactured to oscillate extremely reliably at a particular frequency prescribed by the user, and this frequency will be highly stable, that is, it will not alter appreciably with

_OMPI varying ambient environmental changes. The crystal actually specified oscillates at a frequency of 6 Megahertz (MHz) .

Circuit 32, is a "demultiplexing circuit" which serves to demultiplex the multiplexed bidirectional 5 address/data bus (39). This bus (39) comprises a series of electronic paths via which circuit 30 addresses (or calls-upon) other circuits in the system, and over which data is transmitted to or from circuit 30 and other circuit elements. Circuit 32 may be implemented by a parallel

10 network of D-type latches. Bus 37, is a unidirectional control bus, along which certain control signals are sent from circuit 30 to other elements. Circuit 32 receives information from buses 39 and 37 and demultiplexing of 39 is performed in conjunction with control signals (37) to

15 produce a "demultiplexed address bus" (40) which serves to address certain memory elements in memory arrays 33 and 34.

Circuit 33 is a memory array as first indicated but is the type of memory from which data may be read

2.0 only. It is designated an "erasable-programmable-read¬ only-memory" ("EPROM") and contains the entire micro¬ computer system's control program together with tariff constants required to generate taxi fares for particular regions. Since the EPROM is erasable, the tariff or taxi

25 fare rates may be altered to suit regional requirements by alteration of appropriate constants. These constants are not alterable while circuit 33 is in the "in-circuit" condition. For alteration it must be removed from the circuit board to which it is connected and altered by

30 means of external laboratory equipment.

Circuit 33 is "addressed" by circuit 30 along input address paths 40 and 38, the latter of which is a "multiplexed address/input-output bus". Buses 38 and 40 operate in concert with bus 37 to read data from circuit

35 33, the said data existing circuit 33 via bus 39 from which it is read by circuit 30 for progressing.

Circuit 34 is also a memory array but differs from circuit 33 in that the former (34) is read/write memory, which means that circuit 30 may read from or writ into this memory array. Circuit 34, is addressed by 30 along bus 40 which acts in concert with bus 37. Memory data may pass in either direction between circuits 30 and 34 via bus 39.

Circuit 35 is a battery support system for main¬ taining intact the data in circuit 34 in the eventuality that the entire taximeter is removed from its external power source (say the vehicle battery) . Circuit 35 is implemented as a rechargeable battery system which is constantly trickle-charged during external power applica¬ tion periods to provide up to 6 months of battery back up power in the event of long term external power removal. Circuit 55, comprises a keypad to which 4 buttons are electrically connected. The keypad 55 communicates with circuit 30 via a "bidirectional input-output bus" 36. The keypad 55 provides the medium by which taximeter activity is controlled by the operator. Reference is now made to Fig. 1(b) , -the continua¬ tion of the circuit block diagram represented in Fig. 1(a) Circuit 54 is an array of 8 seven-segment light emitting diode displays and 2 discrete light emitting diode lamps. This array is controlled by circuit 30 via bus 36 and circuits 41 and 42.

Circuit 41 decodes the binary-coded-decimal data present on bus 36 into 7-segment display data for activation of any of the 7 individual elements which comprise a display digit. Data from circuit 41 is presented to each of the 8 digits simultaneously.

Circuit 42 is a "one-of-eight decoder/driver" circuit and is directed by circuit 30, via bus 36, to activate only one of the 8 digits at any moment in time. Hence even though circuit 41 presents the same data to all digits at any moment, circuit 42 activates only the digit which is designated to receive this data as prescribed by circuit 30, and only that designated digit

OM (addressed by 42) will illuminate and indicate data to the operator.

By means of circuits 41 and 42, circuit 30 actually directs the illumination of only one digit (of the array) at any moment in time, where directions from circuit 30 change at least 800 times every second to activate each digit in a cyclic manner at least 100 times a second thereby sequencing the turn-on and turn-off of each digit in a cycle at a rate of faster that 100 times per second, which produces an image to the operator of all digits being illuminated at any one moment. This is a widely practiced electronic technique called "display multiplexing"

Circuit 43 is an "input/output expander" which serves to "expand" the otherwise limited input-output capacity of bus 38. Circuit 43 is controlled by circuit

30 via buses 37 and 38. It is via circuit 43 that circuit 30 may transmit data to, or receive it from other elements such as, for example, 44, 45 and 48 along bidirectional bus 38. Circuit block 44, represents a "dual-in-line switch pack" via which the taximeter may be calibrated for use in individual vehicles. A particular combination of on/off positions of the 8 switches (in 44) represents a binary combination relating to the number of revolutions of the speedometer cable a particular vehicle performs when driven over a standard length of roadway, say 1 kilometre.

The number of said speedometer cable revolutions per kilometre driven will vary from one vehicle to the next, where said number of revolutions is dependant on many factors such as tyre size, tyre pressure, degree of tyre wear, gear box ratio, differential box ratio, and the like. Thus in order to ensure that the taximeter records an accurate fare, the said meter must be initially calibrated for use in that vehicle, where said calibration is effected by selecting appropriate on-off combinations on switch pack 44.

Circuit 45 is a block containing high current

OMPI . WIPO Λ. drive circuits for activation of external indicator lamps such as a taxi's dome light. Circuit 43 provides the appropriate signals (as directed by circuit 30) but the electrical current carrying capability of signals origin- ating from circuit 43 is much too light to effect switchi of the required indicators. Thus circuit 43 controls external indicators via circuit 45 which performs the necessary electrical current amplification required.

Circuit lines 51 are connected to the indicators after passing outside the taximeter via a back panel connector (not shown) . Elements to the left of the dashe line in Fig. 1(b) are housed inside the meter's case, whereas elements to the right of the said line are outsid the taximeter's case, and connected to the meter circuitr via the said connector.

Circuit element 47 is a transducer assembly which converts each revolution of a taxi's speedometer cable (not shown) into 8 sequential electronic signals, which the meter detects to determine distance travelled. The speedometer cable is actually coupled to element 47 which contains a shaft (not shown) adapted to revolve in concer with the cable. A flat disc (not shown) is mounted on th shaft and the disc also revolves with the shaft and cable Eight holes are drilled in the disc close to its outer perimeter and located so that each hole is equidistant fr its adjacent holes around the circumference of the disc. A light emitting diode (not shown) and a photo-sensitive transistor (not shown) are located in the transducer assembly, such that infra red light from the diode shines directly on the phototransistor, which is sensitive to the presence of this light. The disc is aligned so that it rotates through the light beam. When one of the 8 holes is in line with the beam, the light activates the transistor, and conversely when a hole is not in line with the beam, the beam is blocked and the transistor is not activated.

Signals from the said phototransistor are transmi from circuit 47 to circuit 46 (inside the meter) where circuit 46 is a signal-conditioning circuit, such as a "Schmitt-trigger" which conditions said signals for passage to circuit 48. The latter circuit is a "recognition and acknowledgement" circuit (in the form of a "flip-flop") which is controlled by circuit 43, and which directs transducer signals to circuit 30 for processing and counting, via bus 36.

Circuit 49, performs two functions. It accepts power (along line 52) from the vehicle'selectrical source, such as a car battery, and conditions this source for use in the meter. A voltage of between +11 and +14 volts may be present on line 52 during meter operation, and as long as this voltage is between +7 and +30 volts, circuit 49 provides a stable regulated output voltage of +5V to drive all the meter's circuit elements.

Furthermore circuit 49 incorporates a "Schmitt- trigger" circuit to detect voltage fluctuations. When the voltage drops below say +8 volts the trigger shuts the taximeter down by activating line 50, which disenables operation of circuits 30 and 34 and sends these circuits into a standby-non-operational condition whereby the circuits cease to communicate and data is retained in circuit 34 by reans of battery support system 35. When the input voltage (52) again rises above sa +10 volts these circuits (30 and 34) , are re-enabled for operation. Due to the low power requirement of the circuit components, the fact that only the data storage components are powered in the event of main power failure and the trickle charging feature for the auxiliary battery it is possible to retain data for up to six months from disconnection of the main battery supply.

Bus 53 is a bidirectional bus which enables the meter to communicate with external electronic systems such as a receipt printer, should such external options be required.

In order to fully detail how the taximeter operates. it is necessary to describe how the program, lodged in circuit 33, is configured. The basic configuration is shown in Fig. 2, the program flow chart. Circuit 30 reads and processes program instructions in a sequence determined by the program itself, and each instruction is executed in less than 5 millionths of a second by the said circuit.

Upon power application to the meter, circuit 30 begins executing instructions at program item 10 to which it only returns after power has again been applied following a prior break in power input.

The program initialization path can take one of two routes namely:- 10, 11, 12, 13, 14 and 16 or alternatively 10, 11, 15, 14 and 16 as indicated in Fig. 2 This will be further explained later.

Following initialization, circuit 30 begins executing the "main loop" of the program and this loop is indicated by the paths which join program blocks 17, 18, 19, 20, 21, 22, 23, 24 and then back to block 17. This entire loop (or body of program instructions) is executed by circuit 30 approximately once every millisecond. The separate blocks of program instructions contained within this loop, direct circuit 30 to supervise the total opera¬ tion of the meter in all its facets, including:- - control of front panel displays (20)

- recognition of front panel key depressions (18)

- control of external indicators (21)

- calculation of taxi fares (23)

- maintenance of 15 separate items in memory circuit 34, (18, 22, 23) and further, as described later.

The front panel keys (55) provide the means by which the operator may control meter activity, and this includes the starting and stopping of fares, the addition of extras to a fare, the alteration of rate (or tariff) at which fares are calculated, and the display (for purpos of inspection) of individual items from memory.

C...FI

/, IFO The information which may be displayed (on circuit 54) is stored in sequence in memory circuit 34. Even if power is removed from the meter this data is maintained intact since circuit 35 provides enough auxiliary power to maintain this data for up to 6 months.

The list below indicates that circuit 34 is divided into "memory regions" where each region is avail¬ able for the storage of particular items of information. MEMORY REGION (WITHIN CONTENTS CIRCUIT 34)

0 CURRENT FARE DATA

1 DIGITAL CLOCK, INDICATING TIME OF

DAY

2 TOTAL FARES RECORDED ($.<?) 3 TOTAL KILOMETRES TRAVELLED

4 PAID KILOMETRES TRAVELLED

5 NUMBER OF SEPARATE FARES

6 NUMBER OF SEPARATE FARE UNIT

INCREMENTS 7 . NUMBER OF SEPARATE EXTRAS UNIT

INCREMENTS

8 TOTAL ENGAGED TIME (HRS.MINS)

9 TIME TRIP STARTED 10 TIME TRIP ENDED 11 TOTAL KILOMETRES AT TRIP START

12 TOTAL KILOMETRES AT TRIP END

13 CURRENT VEHICLE CALIBRATION

(REVS/KM)

14 SPEEDOMETER CABLE REVOLUTION COUNTER

15 TIME OF DAY ADJUSTMENT MODE

16 INTERMEDIARY CALCULATION RESULTS,

"FLAGS" AND OPERATING PARAMETERS The data stored in regions 2 to δ inclusive is of paramount importance in evaluating the total work done and operating efficiency of the taxi, and this data must be preserved against interference by unscrupulous taxi drivers. This data may be cleared from circuit 34 only if the meter case is opened (after breaking its seal) an a "clip lead" is attached to a line on bus 36 to ground the SYSTEM CLEAR line prior to reapplication, of power following a prior power supply break.

Taxi drivers do not have access to the interior o the meter (because of the seal) and therefore power reconnection after an interruption will not clear circuit 34 of its data because the SYSTEM CLEAR line cannot be grounded from the exterior of the case.

Item 11 in Fig. 2 is processed immediately after power reapplication. This program block has the function of testing the SYSTEM CLEAR line. If it has been grounde program flow passes from block 11 to block 12 wherein circuit 30 is instructed to clear all data from circuit 3 If the SYSTEM CLEAR line is not grounded, the program passes from block 11 to block 15, wherein circuit 30 is directed to retrieve its prior operating data from region 16 of circuit 34, and data in other regions of circuit 34 is left unaltered.

After clearing circuit 34 of its data (block 12) , program flow passes to instruction block 13. This is a complicated program block in which many initializing calculations are performed. Under the direction of instructions located in this block, circuit 30 reads the current vehicle calibration (revol tions/km) from circuit 44 (the switch pack) and stores this information in memory region 13 (circuit 34) . Circuit 30 then sets the tariff to number 1 (the default condition after "system clear") and reads the programmed constants relating to th tariff from circuit 33. In particular circuit 30 reads the number of metres to be travelled to effect a fare increment, and the time elapsed to effect a fare incremen Within block 13, calculations are then performed to determine

(a) the number of transducer pulses to be counte for each 100 metres travelled

(b) the number of said pulses required to effect a fare increment ^^URE

OM

/., WIIPP (c) the velocity at which meter operation and fare calculation changes from time based fare determination to distance based fare determi ation. Once this data is calculated the results are stored for later reference in circuits 30 and 34.

Regardless of which path was followed as a result of the test at item 11, program flow proceeds to blocks 14 and 16 where the "hardware timer" in circuit 30 is initialized to time out every 20 milliseconds. This timer operates in parallel with program execution as described in Fig. 2, and at each 20 millisecond timeout an auxiliary program interrupts the program shown in Fig. 2 and resets the timer immediately for determination of the next 20 millisecond time interval. This auxiliary program also counts the progressive number of 20 milli¬ second time-outs and sets a "flag" in circuit 30 each time h a second has elapsed. This flag is monitored, as described later. The program then enters the "main loop" at instruction block 17. Block 17 has the function of directing input circuitry in circuit 30, to count any transducer pulses (by way of interrupt) which may be present on bus 36 after passage through circuits 46 and 48.

Following this, the program executes from block 18 in which circuit 30 scans the front panel keys, circuit 55, via bus 36. It is via these keys that the meter's operating mode may be altered. Depending on which key is pressed and the sequence of such depressions, program block 18 will set various "flags" and parameters in certain registers contained within circuit 30 for later interpretation by other program blocks within the afore¬ mentioned "main loop" . Such flags or parameters would indicate whether the meter is to calculate a fare or not, and if it is to calculate a said fare, whether fare calculation is to be based only on distance travelled, or alternatively by a combination of both time and distan considerations where fare calculation proceeds according to the faster of the two rates. Likewise such flags or parameters would indicate which memory item was being inspected whilst the meter was not calculating a fare. The program next proceeds to block 19 in which circuit 30 "dumps" the contents of its registers into region 16 of circuit 34. These registers contain flags parameters (such as those set and monitored in block 18) ,. and these are "dumped" into circuit 34 in preparation for an interruption in applied power. It is these flags and parameters that are restored to circuit 30 during execution of block 15 after "non-destructive" power reapplication. Program block 20 is executed next. In this bloc circuit 30 checks its body of flags and parameters and determines which data is to be displayed to the operator via circuit 54. The appropriate data is read from circui 34 and the appropriate digit is illuminated. Only one display digit is illuminated during each passage of the program through block 20 and each digit is subsequently illuminated once every 8 such passages, in a manner described earlier.

Program flow next continues to block 21, where again circuit 30 accesses its internal registers to determine which of the external indicators are to be activated.

Block 22 represents a body of instructions which initially determines whether the meter is being used in its revolution counter mode, and if so the instructions in this block direct circuit 30 to maintain revolution counter operation.

It is in block 23 that the meter actually pro¬ gressively calculates taxi fares. For distance only operation, this program block merely counts transducer pulses and determines whether enough distance has been travelled for another increment in fare. For time/ distance operation this block determines which of the

O two variables is proceeding at a faster rate . It does this by counting the number of pulses in a given time period, say h. second, (equivalent to the speed of the vehicle) and compares this with the change-over speed calculated in block 13 . If the speed determined is faster than the said change-over speed, fare calculation is based on distance travelled; otherwise it is based on elapsed time .

Furthermore block 23 supervises the maintenance of memory data, such as that data stored in regions 1, 2, 3, 4, 6 and 8 of circuit 34.

Program flow then passes to item 24 which checks to determine whether the operator requested a tariff change, i.e. requested fare calculation to be based on an alternative rate. If this was the case the program passes to block 25 wherein calculations (similar to those in item 13) are performed for the requested tariff. Otherwise the program returns to block 17 and the loop is traversed once again. It should be apparent from the description hereinabove that the meter according to the present invention provides a number of advantageous features over previously known electronic taxi meters. For example, calibration of the meter may be readily effected without disconnection of the speedometer cable from the meter. It is possible for the user to obtain an immediate read-out of the current calibration factor and this can be checked merely by driving the vehicle over a measured distance. Furthermore, the use of an erasable memory chip enables alteration to the rate of any of the variables merely by replacement of a single re-usable memory chip. Over the life of a meter this can result in significant savings as there is only a labour component involved in the cost of such a change. Also, the back-up system comprising a miniature battery which is continuously trickle charged enables information to be maintained in the meter for up to six months if the main supply is disconnected and ensures that current

O...PI /Mm WIPO _ mode of operation data is not lost if such a disconnec¬ tion occurs. The operation of this back-up system is greatly enhanced by the unique feature of dumping information from the main microcomputer memory into a number of low power read/write memory devices which require only about one thousandth of the power of the main memory. Since this dumping occurs frequently and cyclically it ensures that the information in the low power memory devices is continuously up-dated. Finally by providing a real time digital clock in the meter there are a number of possibilities available such as measurement of driver efficiency in a more realistic manner and provision for obtaining data necessary for charge account customers. In addition to the above the taximeter according to the present invention is consid to be more reliable than known taximeters since it is has fewer components and uses solid state circuitry exclusively.

c*^Λ-

Claims

1. An electronic taximeter including a microcomputer memory (30) therein, characterized in that, said memory is arranged to store and provide on initiation a read-out to

^■an electronic display (54) of the current calibration factor 5 for which the meter is calibrated, said meter further including an electronic revolution counter adapted to operate in conjunction with said display to provide a count and read-out of the revolutions of a speedometer cable providing input data to said meter, whereby calibra- 10 tion of the meter may be checked by driving the vehicle over a measured distance.

2. An electronic taximeter as defined in claim 1, characterized in that, said read-out is a progressive read-out and said display (54) is an L.E.D. display.

15 3. An electronic taximeter as defined in claim 1 or 2, characterized in that, said calibration factor is changeable by selecting differing combinations on an 8-switch dual-in¬ line package (44) incorporated in electronic circuitry of said meter.

20 4. An electronic taximeter as defined in any one of the preceding claims, characterized in that, said meter incorporates a digital clock frequency source (31) and is adapted to provide, on initiation, a read-out on said display (54) of total engaged time whereby the difference in total engaged time before and after a particular usage of the taxi may be expressed as a fraction of the total time of said usage to provide a determination of driver efficiency.

5_*. An electronic taximeter as defined in claim 4, characterized in that, said meter is adapted to provide, o initiation at the end of a particular fare, the actual tim which said fare commenced and ended and the total distance reading at which said particular fare commenced and ended.

6. An electronic taximeter as defined in any one of the preceding claims characterized in that tariff rates of any variable tariff may be altered by replacement of a single re-programmable and hence re-usable memory chip (33)

7. An electronic taximeter as defined in claim 6, characterized in that, said memory chip (33) is ultra-viol light erasable.

8. An electronic taximeter as defined in any one of the preceding claims, characterized in that, said taximete incorporates a miniature rechargeable battery supply (35) ^■ which is adapted to be continuously trickle-charged when said meter is connected to the vehicle's electrical power supply, said battery supply (35) being adapted to supply sufficient power to said meter to retain therein for a period up to about six months all operating data including current fare data if meter is in use, in the event that said vehicles electrical power supply fails ^"or is disconne and said microcomputer (30) being adapted to ensure that said taximeter automatically resumes operating upon reconn tion of said vehicle's power supply in precisely the same mode in which it was operating prior to said failure or disconnection.

9. An electronic taximeter as defined in claim 8, characterized in that, an array of low power read/write

O..I

/,, WIP memory circuits (34) are connected to said memory (30) and said memory (30) is adapted to cyclically^' dump all current operation mode data into said memory circuits, said memory circuits are also adapted to. retain and up-date all other taximeter data and said battery supply (35) is connected to provide said sufficient power to said low power memory circuits (34) in the event of said failure or disconnection in order to retain said current operation mode data and said all other data therein for said period, said micro- computer memory (30) being adapted to cause retained said current operation mode data to be retrieved from said memory circuits (34) in the event of restoration of said vehicle electrical power supply.

10. An electronic taximeter as defined in claim 9, characterized in that said dump occurs about every millisecond,

O...PI i, WIiFnO-.

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