GB2281460A - Sign failure detection particularly for a taximeter - Google Patents

Abstract

In a micro-processor controlled taximeter 10 with an associated external display unit 14 including a "FOR HIRE" sign 15, the supply ofcurrent to the sign 15 is monitored by a device 20 which provides an output to the micro-processor 11 as a measure of the current flowing in the circuit. When the output of the device 20 indicates that there is no current flowing to the "FOR HIRE" sign 15 when there is a signal at the output 11a of the micro-processor which requires the "FOR HIRE" sign 15 to be displayed, a "sign failure" signal 13a is displayed on a display panel 13 forming part of the taximeter 10. The system may also be used with a public service vehicle destination indicator or a paging system. <IMAGE>

Description

Title:- "Sign failure detection" Description of the invention This invention relates to the detection of a sign failure, particularly in the context of the "FOR HIRE" sign customarily displayed by taxi vehicles plying for hire.

Normally, a taxi vehicle carries a display unit containing an electrically operated "FOR HIRE' sign, usually illuminated by one or more electric lamps, although other types, such as L.E.D. displays may be employed. Other signs, such as "HIRED" may similarly be provided in the display unit.

Operation of the "FOR HIRE' sign is normally controlled from a fare meter (taximeter) such that when the meter is brought into use the "FOR HIRE" sign is extinguished and, where provided, a "HIRED" sign is illuminated.

Conversely, when the taximeter is reset to zero, the "FOR HIRE" sign is illuminated unless overridden, for example when the vehicle is not available for hire.

Failure of the "FOR HIRE" sign can lead to significant loss of business and the present invention seeks to provide a mechanism for making the driver of a taxi vehicle aware of such failure so that it can be remedied with a minimum of delay.

According to the invention we provide in combination with a taximeter having a "display sign" output to control the display of a sign to indicate that the vehicle is available for hire, means for monitoring said sign at least while display thereof is required as a result of said "display sign" output and providing a "sign failure" output in response to the absence of display of said sign, and means for displaying a "sign failure" signal in response to said "sign failure" output.

Where other signs are displayed under the control of respective "display sign" outputs from the taximeter, such other signs may also be monitored in a similar manner to provide an indication of failure.

In accordance with the invention an electrical circuit to said sign includes a detector which monitors current flow to said sign. Preferably, the detector comprises a resistor which is connected in said circuit and means for measuring the voltage drop across such resistor. It will be appreciated that when said sign is displayed the current flowing through the circuit will give rise to a voltage drop across the resistor, whereas when no current is flowing, for example due to failure of an illuminating lamp, there will be no such voltage drop.

In a preferred arrangement where the taximeter includes a microprocessor, the voltage across the resistor is applied to an analogue to digital convertor the output of which provides a measure of the current flowing in said circuit.

The voltage drop across the resistor may be sampled after a fixed time interval after the establishment of the "display sign" output of the taximeter so that, in the absence of an appropriate voltage drop after the time interval the "sign failure" output is generated.

Alternatively, by continuously comparing the detected voltage drop across the resistor in the circuit to said sign with a reference voltage, derived for example from the "display sign" output the micro-processor in the taximeter can produce a "sign failure" output appropriate to whichever sign is intended to be on display.

Such "sign failure" output causes an appropriate message to be displayed on the meter so that the driver is immediately aware that the sign is not on display.

A relay or solid state switching device may be incorporated in the taximeter for controlling operation of the sign, and in that case the current detector can readily be incorporated within the taximeter in association with the relay or solid state switching device, and the micro-processor can readily be programmed to display the required sign failure message. However, in other cases the resistor and associated voltage detection circuitry can be provided externally of the taximeter so as to provide an output which is fed back to the taximeter through an appropriate circuit.

For example, where the relay or solid state device is disposed at a position remote from the taximeter, (such as in the display unit itself or in a separate unit for installation elsewhere in the vehicle) the "display sign" output being supplied thereto by means of a suitable circuit extending from the taximeter to the relay or solid state switching device, the detector may be associated with the relay or switching device or with connecting leads in circuit therewith.

Other signs displayed by the display unit in response to other outputs from the taximeter may be monitored in a similar manner.

The invention further resides in sign display apparatus comprising an electrically energised sign and a control device for controlling the energisation of said sign, said control device being separate from said sign and connected thereto by electrical leads, wherein means are provided for electrically monitoring said sign at least whilst energisation thereof is called for by said control device and providing an indication of absence of energisation of said sign.

Preferably, the indication of absence of energisation of said sign is provided by means of a display unit associated with said control device. The control device may be provided in, or in association with, a taximeter and the sign display apparatus may include a sign to indicate that a taximeter vehicle is available for hire. The control device may also be provided in association with other types of display apparatus, such as a destination indicator of a public service vehicle, preferably in, or in association with, a control unit remote from the sign.

Other features of the invention will become apparent from the following description given herein solely by way of example with reference to the accompanying block diagram.

By way of example, a typical taximeter 10 includes a micro-processor 11 which calculates the fare due for each journey and can be set into a number of different states by manual input from the vehicle driver, e.g. by pressing a corresponding button on a manual input panel 12.

The states typically include "ON", "FOR HIRE", "HIRED" and "STOPPED" and the micro-processor is programmed to provide various output signals to an on-board display panel 13 and an external display unit 14 which is arranged to display at least one sign 15 to indicate that the vehicle is available for hire, and usually a further sign 16 to indicate that the vehicle is hired, although in some cases instead of the separate sign 16 which positively indicates that the vehicle is hired, the "HIRED" state may simply result in the sign 15 being suppressed.

Normally, the signs 15,16 will be illuminated by means of one or more incandescent electric light lamps, or a fluorescent electric lamp, although in some cases the display may be in the form of light emitting diode devices.

Operation of the appropriate buttons on the manual input panel 12 causes the micro-processor 11 to generate a signal at output 11a which is applied to the external display unit 14 to illuminate the "FOR HIRE" sign 15.

When the vehicle has been hired for a journey, operation of the appropriate button on the manual input panel 12 causes the micro-processor 11 to start computing the cost of the journey and also provides a signal at output 1 lib which is applied to the external display unit 14 to suppress the "FOR HIRE" sign 15 and illuminate the "HIRED" sign 16. At the same time, further , puts from the micro-processor 11 display information on the on-board display panel 13 including for example the distance, duration or current cost of the journey being undertaken.

When the journey is completed and the taximeter is reset to indicate that the vehicle is again available for hire, the output at lia is again applied to the external display unit 14 so as to extinguish the "HIRED" sign 16 and reilluminate the "FOR HIRE" sign 15.

The signals at outputs lia and 11bmay operate respective relays RLA and RLB to complete electrical circuits to the display unit 14, or corresponding solid state switching devices. The relay RLA, RLB or equivalent devices are shown as being incorporated within the taximeter 10, but this need not be the case; they may be arranged as a separate unit mounted adjacent to or remote from the taximeter, or they may be incorporated in a display unit 14.

In accordance with the invention a current monitoring device 20 is connected in the supply circuit associated with at least output 1 1a of the microprocessor 11 in order to monitor the current which is supplied for illumination of the "FOR HIRE" sign 15.

The device 20 includes a resistor 21 with an associated analogue to digital convertor 22 which generates a digital output as a measure of the current flowing through the resistor 21 in accordance with voltage drop across the resistor.

The digital output of analogue to digital convertor 22 is fed into the microprocessor 11 as an additional input signal which provides an indication of whether or not the requisite current is being supplied for illumination of the "FOR HIRE" sign 15.

When the input from the manual input panel 12 calls for the "FOR HIRE" sign 15 to be illuminated, by establishment of the appropriate signal at output 11, the software in the micro-processor 11 establishes a predetermined time delay appropriate to the response time of the relay RLA and after the elapse of the predetermined time interval compares the input from the device 20 with a reference value in order to determine whether the "FOR HIRE" sign 15 is illuminated. If the input signal from the device 20 indicates that there is no current flowing through the resistor 21, and the "FOR HIRE" sign 15 is not illuminated, the software causes a "sign failure" display 13a to be shown on the on-board display panel 13.The signal from the device 20 may be compared with the reference value either continuously after the expiration of the predetermined time interval, or during only a second predetermined time interval.

If desired, the "HIRED" sign 16 may be monitored in a similar way by a further current detection device associated with output 1 1b of the microprocessor.

The resistor 21 may be located within the taximeter, but may alternatively be located externally of the taximeter 10 as shown, for example in association with the electrical leads between the relays and the display unit 14.

This arrangement is particularly advantageous in that it enables the value of the resistor to be chosen as most appropriate for the form of illumination employed in the display unit. Where the relays are not provided in the taximeter itself, the resistor 21 (and possibly the converter 22) may be provided in physical association with the relays as a separate unit, either separate from or as part of the display unit 14.

It will be appreciated that where the invention has been illustrated particularly as applied to a taximeter, it may be used with other display devices than for taxi vehicles, in particular destination display signs of public service vehicles may be monitored in a similar manner, and also paging systems and the like which display variable information at one or more positions remote from a control unit, where it is advantageous to have an indication at the control unit of the failure of a remote display unit.

The features disclosed in the foregoing description, or the accompanying drawing, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (12)

CLAIMS:

1. In combination with a taximeter having a "display sign" output to control the display of a sign to indicate that the vehicle is available for hire, means for monitoring said sign at least while display thereof is required as a result of said "display sign" output and providing a "sign failure" output in response to the absence of a display of said sign, and means for displaying a "sign failure" signal in response to said "sign failure" output.

2. A combination according to Claim 1 wherein said monitoring means includes a detector which monitors current flow in an electrical circuit to said sign.

3. A combination according to Claim 2 wherein the detector comprises a resistor which is connected in said circuit and means for measuring voltage drop across said resistor.

4. A combination according to Claim 3 including a micro-processor, the voltage across the resistor being applied to an analogue to digital convertor the output of which provides a measure of the current flowing in said circuit.

5. A combination according to either one of Claims 3 or 4 wherein the voltage drop across said resistor is sampled after a fixed time interval after the establishment of the "display sign" output of the taximeter so that, in the absence of an appropriate voltage drop, after the time interval the "sign failure" output is generated.

6. A combination according to either one of Claims 3 or 4 wherein the voltage drop across said resistor is continuously compared with a reference voltage.

7. A combination according to anyone of the preceding claims wherein said "display sign" output is applied to a switching device incorporated in the taxi meter for controlling the flow of electric current to said sign.

8. A combination according to Claim 1 and substantially as hereinbefore described.

9. Sign display apparatus comprising an electrically energised sign and a control device for controlling the energisation of said sign, said control device being separate from said sign and connected thereto by electrical leads, wherein means are provided for electrically monitoring said sign at least whilst energisation thereof is called for by said control device and providing an indication of absence of energisation of said sign.

10. Apparatus according to Claim 9 wherein the indication of absence of energisation of said sign is provided by means of a display unit associated with said control device.

11. Apparatus according to Claim 10 wherein the control device is provided in, or in association with, a taximeter and the sign display apparatus may include a sign to indicate that a taximeter vehicle is available for hire.

12. Any novel feature or novel combination of features disclosed herein and/or as shown in the accompanying drawing.