The present invention relates to an apparatus for use when utilizing services offered for a certain time in dependence on a prepaid amount, comprising a main unit including an electronic control unit and a time storage for storing of value points representing a prepaid utilization time which, during operation, is counted down under the control of the control unit. Such an apparatus may find its application in many different fields where it is the question of the use of services which can be utilized for a certain time in dependence on a prepaid amount, e.g. in connection with individual parking meters, pay-television or the like, and various other forms of energy supply, such as gas supply through gas meters, etc. When using the apparatus in connection with energy supply, for instance gas supply, it will in practice be combined with a suitable trigger, e.g. a reed relay, providing for disconnection or shut-off of the gas supply when the prepaid time is consumed. Generally there may also be provided a suitable indicator showing operational information of interest, for instance that the utilization time approaches the end or is consumed.

A field of utilization of particular interest is in connection with individual parking meters, that is a parking 5 meter which is intended to be fitted in vehicles so as to be visible for inspection from the outside. In such a parking meter the time storage contains a prepaid parking time, and there is provided a suitable display means displaying parking information of interest, such as remaining parking time, topical o parking zone, etc. The present invention will be described in connection with this field of utilization.

An individual parking meter of the above-mentioned type is known for example from US patent specification No. 4 730285. This known parking meter includes a disposable parking 5 time storage which can not be renewed and reused after purchase of the parking meter when the parking time is consumed. Th parking meter is designed as a plastic card wherein the compo¬ nents of the parking meter together with its electrical batter are embedded. A substantial advantageous feature of such

parking meter is that it represents a completely autonomous system, which implies that when the individual customer or user has bought his parking meter (parking card), no connection between the charge-collecting authority and the user is required at a later time, and no backup or supporting system of any kind is required. However, the fact that the parking time storage can not be renewed and reused after purchase of the parking card when the parking time is consumed, results in increased operational costs for the user, since he has to buy a complete new parking card when the time storage is empty. Further, such a card has to be discarded even if the battery contained therein is not exhausted, something which is inadvantageous with respect to the battery utilization, and also represents an environmental drawback if the card is only thrown away after use. s It is an object of the invention to further develop the above-mentioned known parking meter in such a manner that the above drawbacks are avoided.

A further object of the invention is to provide an apparatus of the stated type resulting in reduced operational 0 costs to the user in that the time storage may be refilled, and wherein the apparatus still represents a completely autonomous system.

A more particular object of the invention is to provide an individual parking meter giving the charge-collecting 5 authority greater flexibility with respect to amount of parking fee and offer to the user as regards the size and price of a refill.

The above-mentioned objects is achieved with an apparatus of the introductorily stated type which, according to o the invention, is characterized in that the main unit is arranged for connection thereto of a separate refill unit which, in cooperation with the control unit, causes refilling of the time storage with a chosen number of value points, that the refill unit constitutes a part of the main unit necessary for the 5 operation thereof and is constructed so as to be usable for said refilling only once, and that the control unit is arranged not to allow refilling of the time storage beyond a chosen maximum number of times when connecting successive fresh refill units to the main unit.

It is also an object of the invention to provide a device enabling refilling of the time storage of an apparatus of the type stated in the introduction at the same time as an autonomous system is retained. According to the invention said object is achieved in that the device consists of a refill unit which is arranged to be plugged into the main unit and including a circuit means which, in cooperation with the control unit of the apparatus, causes refilling of the time storage with a chosen number of value points, the circuit means being designed so as to consti¬ tute a part of the main unit necessary for the operation thereof, and such that it may be used only once for said refilling.

By means of the solution according to the invention considerably lower operating costs are obtained for the user. This is mainly due to the fact that the investment in the apparatus itself will be a one-time investment, and that the user thereafter only has to buy the refill unit. This will be substantially cheaper to manufacture than the main unit, so that the price thereof will only be a fraction of the price of the main unit.

The system still will be completely autonomous and not need any backup system, since the refill unit will become the value carrier of the system and can be bought in any shop o kiosk. In an advantageous embodiment of the apparatus according to the invention the control unit is arranged t recognize at least two different types of refill units represen¬ ting a different number of value points. Thereby, when th apparatus is adapted to be used as an individual parking meter, a greater flxibility is obtained for the charge-collectin authority (e.g. a city or municipality), since the user the may be offered various refill versions, whereas the parkin card itself is still the same. For example, refill units o two different values may be offered. The refill unit in practice may be manufactured i accordance with two alternative solutions, viz.' with a batter or without a battery. There will be little or no limitation i storage time of the battery-equipped refill unit, the unit onl consuming current of importance after interconnection with th

main unit. This results in reduced stock investments.

The invention will be further described below in connection with exemplary embodiments with reference to the drawings wherein the apparatus constitutes an individual parking meter, and wherein

Fig. 1 shows a circuit diagram of a refill unit provided with a battery, and wherein the refill unit is shown in connection with a parking meter main unit which is schemati¬ cally shown as a block diagram; o Fig. 2 shows a circuit diagram of a refill unit which is without a battery and is shown in connection with a parking meter main unit in a manner corresponding to Fig. 1; and

Fig. 3 shows an example of an embodiment of a parking meter consisting of a card-shaped main unit having a refill s unit plugged therein and placed in a recess in the main unit.

The diagram in Fig. 1 shows a refill unit 1 which is connected to a parking meter main unit 2, the latter being adapted for mechanical and electrical connection thereto of the refill unit, as further described below. The refill unit is o provided with a battery Bl (3 volts) and is constructed around two integrated circuits IC1 and IC2 connected in the manner appearing from Fig. 1. IC1 is of the type 4093 and is a so-called CMOS quad 2-input NAND Schmitt trigger, and IC2 is of the type 40107 and is a so-called CMOS dual 2-input NAND 5 buffer/driver. IC1 contains a pair of flip-flops having two different stable conditions, and wherein one condition is used prior to connection of the refill unit ("start" of the parking meter), and the other afterwards. IC2 has for its task to discharge the battery when the refill unit is disconnected from o the main unit. This IC contains two ports and a drive stage to draw the necessary current for the battery discharge. In the reality, only one half of the IC2 is used, as appears from Fig. 1 wherein the pins 5, 6 and 7 are omitted in IC2.

A detailed description of the circuit construction of 5 the refill unit is considered to be unnecessary, since the utilized connections and circuit chips will be well known to a person skilled in the art. Here it should only be remarked that the lines terminating in an outwardly directed arrow symbol are connected to the plus terminal of the battery via

the illustrated line having an arrow symbol directed towards the battery. In other respects the function of the different components will be further described below in connection with the description of the operation of the unit. The main unit 2 of the parking meter is of the introductorily stated type and includes as illustrated a control unit in the form of an electronic processor 3, a parking time storage 4 and a display 5 which is controlled by the processor and is supplied with driving current through a driving stage 6. Even if the Figure shows only said main components of the main unit 2, it is to be appreciated that this also comprises additional components as described in the aforementioned US patent specification No. 4 730 285, i.a. operating elements in the form of an ON/OFF button and a zone selector button for the s choice of correct parking zone. For a further description of the general operation and construction of the parking meter reference is made to said patent specification.

The main unit also contains a battery (not shown) providing for current for backup of the processor. However, o the display 5 of the main unit is driven by the battery Bl in the refill unit, as appears from the connection in Fig. 1. Thus, the refill unit must be connected to the main unit in order for the display to function, and the refill unit thus constitutes a part of the main unit necessary for the operation 5 thereof. This contributes to the security of the system and therefore is an important feature in practice.

The electronic components and the battery of the refill unit advantageously are embedded in a plastics wafer which is so designed that the wafer will be destroyed if a 0 person tries to open it to replace the battery. The main unit, in turn, is in the form of a plastics card wherein the components of the unit are embedded. In one side of the card there is provided a drawer-shaped recess which is adapted to receive the plastics wafer constituting the refill unit. Such an arrangement 5 is shown in Fig. 3 wherein a card-shaped main unit 7 is provided with a recess 8 in which there is placed a refill unit in the form of a flat wafer 9. As appears from the Figure, the refill unit, when it is in place in the recess 8 and plugged into th main unit, constitutes a part of the surface of the main unit.

Further, in the illustrated example, the surface of the plastics wafer 9 is provided with a portion of a logo, the rest of the logo being placed in the surface of the main unit, so that the logo becomes incomplete when the main unit is without the refill unit. In this manner a parking meter guard gets a visual indication that the parking meter, when this is in use in a vehicle, is provided with the "correct" refill unit.

In Fig. 3 there are also shown the display 5 of the parking meter together with an ON/OFF button 10 and a zone selector button 11.

The interconnection between the main unit and the refill unit takes place by means of a suitable plug connection. For example, there may be used contact pins or possibly contact springs in the main unit, and a socket or card edge on the refill unit. In Fig. 1 the interconnection means is shown to comprise seven pins which are marked "1" to "7".

As regards the control unit of the main unit, this consists, as mentioned, of a processor which is adapted and programmed for execution and control of the necessary parking 0 meter functions. When connecting the refill unit, the processor is arranged to deliver a number of pulses to the refill unit and to carry out a comparison of the emitted pulses with return pulses from the refill unit, and to approve the refill unit for refilling of the time storage if the returned pulses are 5 recognized by the processor within a chosen time period. In this manner the processor controls with a reasonable degree of security that the refill unit is not a fake. Further, the processor is arranged to count the number of refills, and is programmed in such a manner that it prevents refilling of the o time storage beyond a chosen maximum of times, for example ten times.

If value points are left in the time storage at the time of a refill, the new value which is supplied by means of the refill unit, is added to the value which is left in the 5 time storage.

As regards the refill unit, there will be, as mentioned above, two different types representing a different number of value points, for example 400 or 800 value points. The processor of the main unit is arranged to recognize the topical refill

type in that two different pulses are present on a separat pin out from the main unit. The refill unit then will convey one or the other of the pulses, more specifically through the pins 2 or 3 in Fig. 1, one or the other of these pins being connected, dependent on the type of refill unit.

The operation of the refill unit 1 when it is connected to and disconnected from the main unit 2, will be described below.

When connecting the battery Bl, the refill unit takes up a compulsory condition in which pin 1 = 0 V, ICl pin 12 = 0 V and IC2 pin 3 = +3 V, i.e. no current passes through resistor

R8. When the refill unit is plugged into the main unit, the processor sends a pulse series to the pins 2 and 3. Pin 2 or pin 3 conveys the pulses which are inverted in ICl and sent in s return to the main unit on pin 1. The pulse time is, for example, 3 seconds. The processor recognizes the pulses and places a signal of +3 V on pin 4 (Defect in) which charges the capasitor C5 through the resistor R5. The values of R5 and C5 are chosen so that there is achieved a suitable time constant o and a charging time of approx. 1 second. The length of the

Defect signal should be at least 2 seconds. This signal results in that ICl pin 3 and pin 12 get a high value equal to +3 V, and that ICl now is brought into a state of connection wherein additional pulses from the main unit are not allowed to pass, 5 ICl pin 3 now being +3 V permanently.

The processor now has recognized and approved the refill unit, and the time storage then is supplied with the topical number of value points whereafter the processor lights the display showing the number of value points after refilling. 0 Voltage to the display is applied across the pins 5 and 6. The series resistor R6 prevents that the battery Bl may be shorted from outside.

As mentioned, the refill unit retains its state o connection even if it is disconnected from the main unit. 5 Thereby it is prevented that the refill unit may be used severa times to activate the main unit and refill the time storage.

When disconnecting the refill unit from the mai unit, one has that ICl pin 12 = +3 V. However, in the connecte condition IC2 pins 1 and 2 are forced to 0 V by the pins 6,

because of the illustrated short-circuiting connection in the main unit. When pin 7 is released from 0 V when disconnecting the refill unit, IC2 pins 1, 2 become equal to +2,5 V through R7 (ICl pin 12 = +3 V). IC2 pin 3 then becomes 0 V and will discharge the battery through R8 (100 Ω). The battery then will be discharged in the course of a couple of hours (2 - 5 hours).

As regards the remaining resistors and capacitors in the refill unit in Fig. 1, these in all essentials have as their task to define correct voltage levels in relation to the IC circuits. The capacitor C3 is the time-determining link, a delay of the level on pin 13 being obtained, and the capacitor further provides that ICl positions itself in the desired condition when the battery is connected. A refill unit which is without a battery will now be described with reference to Fig. 2. The Figure shows a refill unit 12 which is connected to a main unit 13. In a manner corresponding to that of Fig. 1 the main unit 13 includes a processor 3, a time storage 4, and a display 5 with associated driving stage 6. In addition, the main unit contains a battery B2 providing for supply of current to the processor as well as the display and the electronic circuit in the refill unit 12.

The refill unit 12 in this embodiment is connected to the main unit 13 through a plug means comprising 6 pins which are marked "1" to "6". The refill unit contains a first transistor stage Tl which, in a manner corresponding to that of ICl, returns pulses from the processor 3 in inverted condition. Further, the refill unit contains a second transistor stage T2 forming a power output providing for burning-off of a fuse Fl, so that the refill unit can be used only once.

The operation of the refill unit when it is connected will be briefly described below.

When the refill unit is connected, the processor 3 sends in pulses on pin 4. The pulses are inverted in Tl and returned to the processor on pin 6. In a manner corresponding to that described in connection with Fig. 1, the processor thereafter sends in a Defect signal = +3 V on pin 3. The transistor T2 starts conducting and shorts +3 V (on pin 2) and 0 V (on pin 5) through the fuse Fl which burns off. The

transistors Tl and T2 thereby will be without 0 V, and pin 6 (Data out) gets a constant high value = +3 V through the resistor R5. Thereafter the processor 3 works in a manner corresponding to that described above. As appears from Fig. 2, the refill unit also in this case is a part of the main unit necessary for the operation thereof, since the supply of current to the driving stage 6 of the display 5 goes through the pins 1 and 2 of the refill unit 12.