GB2096812A

GB2096812A - Validation of coins and tokens

Info

Publication number: GB2096812A
Application number: GB8105079A
Authority: GB
Original assignee: Appliance Components Ltd
Current assignee: Schneider Electric Controls UK Ltd
Priority date: 1981-02-18
Filing date: 1981-02-18
Publication date: 1982-10-20
Also published as: GB2096812B

Abstract

Coins to be examined and/or validated are deposited into a chute (2, 5) defining a guide passage (8). First and second inductive coils (4) are supported on opposite sides of the guide passage (8). A sensor head (3) having a front profiled surface (9) faces the passage (8) and a stop (7) is provided to arrest a deposited coin (6) within the passage such that the coin rests against the profiled surface (9). The surface (9) is shaped such that the spacing between the coin (6) and the surface (9) depends upon the thickness and diameter of the coin. With the coin held in position against the profiled surface (9) one or both of the inductive coils (4) is energised to subject the coin to one or more electromagnetic signals and produce an output indicative of the effect of the coin on the or each electromagnetic signal. As the coin is held stationary whilst measurements are made a high degree of accuracy can be achieved. <IMAGE>

Description

SPECIFICATION Improvements in or relating to the validation of coins and tokens The present invention relates to a method and apparatus for examining coins.

Coin-operated devices such as vending systems include means for checking the authenticity of coins deposited therein and for recognising the value of the coin. Frequently the validation and recognition system is also capable of accumulating the value of a number of coins inserted and only enables the vending system to release goods or continue its operation when a predetermined total value of coins has been inserted.

According to a first aspect of the present invention there is provided a method of examining coins comprising the steps of holding a coin to be examined at a predetermined position, and subjecting the coin held at said predetermined position to at least one oscillating electromagnetic signal to produce an output indicative of the effect of the coin on the or each electromagnetic signal.

Throughout this specification the term "coin" is used to refer to genuine coins and/or tokens, counterfeit coins and/or tokens, and slugs, washers and the like which may be used to try to obtain operation of a coin-operated device.

Coin validation systems in which the coin is subjected to one or more electromagnetic signals are known. However, in the prior art systems the coins move along a guide path past or between sensing coils and the change induced by the moving coin is detected and measured to thereby indicate parameters of the coin. In a method of the present invention the coin is held stationary whilst measurements are made and accordingly the present invention is capable of a greater degree of accuracy than the known system. In addition, the measurements can be repeated and the results averaged to provide an even greater degree of accuracy. The use of such an averaging technique also enables the method to produce accurate results, even if problems, such as noise, arise.

Furthermore, as the method of the invention does not require movement of the coin along a predetermined guide path a device for performing the method of the invention can be made much smaller in size than known devices and there is also less risk of jamming.

Preferably, the coin is subjected to a number of electromagnetic signals having different frequencies such that different parameters of the coin are examined. For example, the coin may be subjected to a high frequency signal, that is, having a frequency greater than or equal to 100 KHz, such that there is substantially no penetration of the signal into the coin. Thus, the high frequency signal "looks" at the surface of coin and can be used to provide a measurement of dimensions of the coin.

Additionally and/or alternatively, the coin may be subjected to a low frequency signal, for example having a frequency in the range 1 H2 to 75 KHr Such a low frequency signal penetrates into or through the coin and can be used to provide a measurement of the characteristics of material of the coin. In an embodiment, the coin is subjected to two low frequency signals. The first signal is at a frequency in the range 1 to 75 KHz and is chosen to be primarily affected by the bulk conductance of the material of the coin. In an embodiment, the frequency is 7.812 KHz. The second signal is in the range 1 H2 to 1 KH2 and is chosen to be primarily affected by the relative permeability of the material of the coin. In an embodiment, this second frequency is 122 Hz.

The oscillating electromagnetic signals are preferably generated by energising one or more inductive coils positioned near said predetermined position. The or each inductive coil may be energised at different frequencies consecutively or the or each coil may be energised at different frequencies simultaneously, for example, by a complex waveform several different frequencies.

In an embodiment the coin is held at said predetermined position against a profile arranged such that one or more, dimensions of the coin determine the spacing of said coin from a first inductive coil.

A high frequency signal, for example, of 500 KHz may be applied to said first inductive coil to give an indication of the spacing of the coin from the first inductive coil whereby the dimensions of the coin can be determined.

The profile may be stepped and/or curved and the coin is arranged to rest against the profile when the coin is held at said predetermined position. Where the profile is stepped the size and spacing of the individual steps may be chosen such that each different acceptable coin rests on a different corresponding step. As each coin is spaced at a distance from the first inductive coil which is determined by its dimensions, it will be appreciated that a measurement of the spacing can be made to enable the dimensions of the coin to be determined.

Where the dimensions of the coin are to be determined by a measurement of the spacing of the coin from the first inductive coil it is preferred that the inductive coil has a diameter which is smaller than the diameter of the smallest of the acceptable coins such that there is no "edge effect".

In a further embodiment the coin is held at said predetermined position adjacent a first inductive coil having a diameter greater than that of the coin to be examined.

An oscillating signal applied to the coin will enable the area of the first inductive coil covered by the coin to be determined and the diameter of the coin can thereby be determined.

The present invention also extends to a method of determining one or more dimensions of a coin comprising steps of holding the coin or token against a profile arranged such that the dimensions of the coin determine the spacing of said coin from a first inductive coil, energising said first inductive coil at a predetermined frequency to subject the coin to an oscillating electromagnetic signal at said predetermined frequency such that the effect of the coin on said electromagnetic signal is indicative of the spacing of the coin from the first inductive coil.

Preferably, the first inductive coil is spaced from a second inductive coil to define a passage therebetween in which said predetermined position is at least partially located.

The invention also extends to apparatus for examining coins comprising means for holding a coin to be examined at a predetermined position, and means for subjecting the coin held at said predetermined position to at least one oscillating electromagnetic signal.

It will be appreciated that the coin will induce changes in the oscillating electromagnetic signal(s) to which it is subjected. As the coin is stationary whilst the signals are applied, the signals will be attenuated by the coin. Of course, the amplitude of the signals and thus the degree of attenuation effected by the coin can be measured simply and accurately. This is in contrast to known systems in which the coins move past the inductive coils and thereby induce a frequency shift. It is more difficult to detect and accurately determine a frequency shift than a change in amplitude and accordingly the method and apparatus of the invention is capable of greater accuracy than the known systems and the detection and measurement circuits required are simpler and therefore less expensive to produce.

Where a coin is to be validated it is necessary to compare the parameters of the coin either with those of an authentic coin or with reference values. Measurement circuits are preferably provided to detect said output indicative of the effect of the coin and compare the output with stored reference values. Preferably, a range of reference values are stored corresponding to each detected parameter of a coin such that allowance is made for wear of the coins and other factors which may change the parameters of acceptable coins. Of course, the size of each range must be set to enable validation of most authentic coins whilst preventing validation of unacceptable coins.

With the present invention the attenuation of each electromagnetic signal caused by the coin under examination may be measured and compared with stored reference values.

In an embodiment, one inductive coil is energised at a first frequency when no coin is held at said predetermined position and the amplitude of the oscillating electromagnetic signal generated by said coil is detected, said one inductive coil is energised at said first frequency when a coin to be validated is held at said predetermined position and the amplitude of the oscillating electromagnetic signal generated by the coil is detected, the ratio of said two amplitudes is then compared with a reference value.

As it is the ratio of the two amplitudes which is compared with the reference value the validation of the coin is independent of any variations in the amplitude of the first frequency. Preferably, a range of reference values associated with said first frequency is stored for comparison with said ratio.

Generally, each coin will be subjected to a number of oscillating electromagnetic signals at different frequencies which may be generated consecutively and/or simultaneously. For each frequency the ratio of the amplitude of the signal with the coin present to the amplitude of the signal with no coin present is compared with a corresponding reference value. If all the ratios associated with one coin fall within the corresponding preset reference value ranges, the coin is acceptable.

Preferably, it is arranged that with no coin at said predetermined position the inductive coil is cyclically energised at a number of predetermined frequencies and that the amplitude of the oscillating electromagnetic signal at each frequency is measured and stored. This process is continuously repeated so that the stored amplitudes are automatically updated to compensate for any change in the amplitudes.

When a coin is deposited such that it moves towards the predetermined position measurement of the amplitude of the oscillating electromagnetic signal at each predetermined frequency with the coin at said predetermined position is automatic'ally initiated after a preset delay period.

In this respect the arrival of a coin will produce a change in the last amplitude measurement made much greater than the updating changes and this is used to initiate the coin validation measurements. Accordingly, it is not necessary to provide separate means to detect the arrival of a coin and initiate validation thereof as in previously known systems.

The detection and measurement of the amplitudes, the formation of the amplitude ratios and their comparison with reference values is preferably performed electronically, for example individual logic circuits or a microprocessor may be used. The electronic circuit provided is preferably arranged also to control the system.

The electronic circuit and the techniques to be used are conventional and are therefore not described herein.

According to a further aspect of the present invention, there is provided a method of validating a coin, comprising the steps of holding a coin to be validated at a predetermined position, subjecting the coin to an oscillating electromagnetic signal at a first frequency and detecting the amplitude of said signal, and comparing the ratio of said detected amplitude to the signal amplitude at said first frequency when na coin is present with a reference.

Preferably, the coin to be examined and/or validated is deposited within a coin chute having a passage defined between two inductive coils. A shaped profile is located within the passage and stop means are provided for arresting a coin deposited in the chute such that the coin rests against the profile. The profile is arranged such that the thickness and/or diameter of the coin determines the spacing of the coin from one of said inductive coils. A control and measurement circuit is arranged to generate signals for energising one or both coils and for detecting an output indicative of the parameters of the coin.

Preferably, the control and measurement circuit is electronic and is arranged to measure the output or compare the output with a preset reference.

The circuit also includes means for actuating the stop means to release the coin once the examination and/or validation process has been completed.

The present invention also extends to a coin deposit chute for a coin validation system, the chute comprising a passage for receiving a coin defined between two inductive coils, a shaped profile located within said passage, and stop means for holding a coin deposited in said chute against the profile, wherein the profile is shaped such that the thickness and/or diameter of the coin determines the spacing of the coin from one of said inductive coils.

Preferably, said stop means comprises first and second solenoid operated stop members; the first stop member being operable to direct the coin held against the profile into a first channel and the second stop member being operable to direct the coin held against the profile into a second channel.

The invention also extends to a coin validation system incorporating a coin deposit chute as defined above and an electronic control and measurement circuit for energising one or both of the inductive coils and detecting the effect of a coin held against the profile on the signals generated by the coils.

An embodiment of the present invention will hereinafter be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a longitudinal section of a coin deposit chute for a coin validation system, Figure 2 showns a section of the chute taken along the line A-A of Figure 1, Figure 3 shows a plan view of the front surface of a sensor head of the chute of Figures 1 and 2, Figure 4 shows a longitudinal section of the sensor head, Figure 5 shows a plan view of the back surface of the sensor head, and Figure 6 shows schematically a circuit diagram of an electronic control and measurement circuit for the coin validation system.

Figures 1 and 2 show a coin deposit chute into which coins are deposited for validation. This chute together with an appropriate control and measurement circuit will generally be incorporated in a coin operated device such as a vending system.

The chute comprises tvvo spaced plates 2 and 5 arranged adjacent one another to provide a guide passage 8 for a coin therebetween. As can be clearly seen from Figure 1, the facing surfaces of the plates 2 and 5 are preferably grooved to define the guide passage 8 and to prevent lateral movement of the coin. The plates 2 and 5 are mounted to extend vertically or at an angle to the vertical such that a coin inserted through a coin entry cup 1 supported at the top of the plates will fall along the guide passage 8 under the effect of gravity.

A circular sensor head 3 is inserted in and supported by the plate 2 and has a front profiled surface 9 which faces into the passage 8. This sensor head 3 supports a first inductive coil 4. A second inductive coil 4 is supported by the second plate 5 such that the two coils 4 are arranged on opposite sides of the guide passage. Two flaps 7 are hingedly mounted on the facing surface of the plate 2 or the plate 5 to define a V-shaped stop having its apex aligned with a predetermined position near the bottom of the surface 9. The two flaps 7 preferably define a 900 angle and the bisector of the angle extends substantially diametrically of the circular profiled surface 9. The width of each flap 7 is sufficient to prevent a coin 6 within the passage 8 falling below the flaps 7 when they are in the stop position illustrated.

The sensor head 3 can be seen more clearly in Figures 3 to 5. The sensor head 3 has a peripheral ring 10 for engagement with the circular rim of an aperture 11 of the plate 2. The front surface 9 of the head 3 is profiled as can be seen in Figures 3 and 4. The curvature of the profile surface 9 is chosen such that when each coin of a set of coins which are to be validated by the system rests against the surface 9 the spacing between the coin 6 and the surface 9 will depend upon the thickness and diameter of the coin. As an alternative to the curved shape of the surface 9, the surface 9 may be provided with a number of individual steps whose spacing and size are chosen such that each acceptable coin of a set of coins rests on a different corresponding step. The rear surface of the sensor head 3 supports the first inductive coil 4.

It will be appreciated that the coils 4 must be insulated from the other components of the chute. Preferably, the plates 2, 5 the sensor head 3 and the flaps 7 are all made of a plastics material.

In use, a coin 6 is placed in the entry cup 1 and then falls along the passage 8 under the action of gravity until arrested by the stop formed by the flaps 7. If the coin is substantially circular the V-shaped stop ensures that the centre of the coin lies on the bisector of the angle defined by the two flaps 7. The arrested coin 6 comes to a stop resting against the profiled surface 9 as shown in Figure 2. In this respect, the chute is preferably mounted at an angle to the vertical such that gravity aids in the location of the coin against the surface 9.

Whilst the coin 6 is held in the position shown in Figure 2 parameters of the coin are measured using electromagnetic signals as will be described hereinbelow. The measurements are initiated and processed by the control and measurement circuit.

If the coin is found to be acceptable one of the flaps 7 is pivoted downwardly about a transverse axis to cause the coin to fall into an accept channel 12 defined by the plates 2, 5. If the coin is not validated the other one of the flaps 7 is pivoted downwardly about a transverse axis to cause the coin to fall into a reject channel 13 defined by the plates 2, 5. In known manner a coin passed to the reject channel 13 may be fed to a coin return chute. Also in known manner a coin passed to the accept channel may either enable operation of the coin-operated device or may have its value entered into an accumulator arranged to enable operation of the device when a predetermined total has been accumulated.

The coin 6 is examined and/or validated by way of oscillating electromagnetic signals generated by the or each coil 4. It is well known that signals of different frequencies will penetrate the coin to different extents, and are thus responsive to different parameters of the coin. Each signal will be attenuated by the coin. Accordingly, the coin is subjected to one or more electromagnetic signals at different frequencies and the effect of the coin on the or each signal is detected. The number of tests performed on each coin is chosen in accordance with the degree of discrimination required. The frequencies of the electromagnetic signals are chosen in accordance with the parameters of the coin it is required to test.

In one embodiment, which gives a very high degree of discrimination, four parameters of the coin are measured, namely: 1 ) Diameter of the coin 2) Thickness of the coin 3) Bulk conductance of the material of the coin 4) Relative permeability of the material of the coin.

As has been made clear above, when the coin 6 rests against the profiled surface 9, the spacing of the coin 6 from the surface 9 and hence from the coils 4 is determined by the thickness and the diameter of the coin. Accordingly, these parameters can be measured by determining the spacing. If one of the coils 4 is energised at a frequency sufficientiy high such that the electromagnetic signal generated by the coil does not penetrate into the coin the high frequency signal effectively "looks" at the surface of the coin and is therefore indicative of its spacing from the coil. Thus, the amplitude of the electromagnetic signal to which the coin is subjected is indicative of the thickness and diameter of the coin.

In an embodiment one of the coils 4 is energised at a frequency of 500 KHz and the amplitude of the signal on that coil is measured.

Subsequently, the other coil 4 is energised at a frequency of 500 KHz and the amplitude of the signal on said other coil 4 is measured. These two measurements 'enable both the diameter and the thickness of the coin to be determined.

Subsequently, one of the coils 4 is energised at one or more lower frequencies such that the generated signal penetrates the coin. In this case the energised coil acts as a signal transmitter and the second coil acts as a signal receiver. The amplitude of the signal can be measured at the second coil. One or more such lower frequency signals may be generated as required and they may be applied consecutively or simultaneously.

As an example, a complex waveform containing a mixture of 7.812KHz and 122 he was used to energise the coil 4 and the signal was sensed by the other coil. The frequency 7.812 KHz is primarily affected by the bulk conductance of the material of the coin and the frequency 122 Hz is primarily affected by the reiative permeability of the material. Accordingly, measurement of the amplitude of the signal at the second coil enables both these parameters to be determined.

A schematic circuit diagram of the control and measurement circuit is shown in Figure 6. The circuit includes signal generating and shaping circuits 14 which generate signals at the frequencies required. These signals are then fed to the coils 4 by mixing and switching circuits 1 5 in accordance with a predetermined test program stored in a central control and arithmetic unit 1 6.

In the example given above a 500 KHz signal is first fed to one coil 4 and subsequently fed to the second coil 4. Thereafter the complex waveform is fed to the one coil 4. The amplitude of each signal is detected on the appropriate coil by way of switching and detection circuits 1 7. A converter 1 8 feeds the data to the central control and arithmetic unit 1 6 for processing. As will be described below, the unit 1 6 compares the data with reference values stored in a register 1 9 and at the end of the test provides a coin accept or a coin reject output which operates one oF the flaps 7 for example by way of a respective solenoid.If the coin has been accepted the unit 1 6 recognises the value of a coin having the measured parameters and enters this value in an accumulated credit register 20.

The circuit illustrated includes a conventional microprocessor and other conventioinal circuits.

As its structure and operation will be apparent to anyone skilled in the art it is not further described herein.

The actual measurements made by the control and measurement circuit and the method of their processing may be chosen as required by suitable programming. However, it is preferred that amplitude ratios be compared with the stored reference values in register 1 9 as this enables the system to automatically correct for variations in amplitude of the signals applied to the coils.

Thus, the circuit is arranged to continuously apply test signals to the coils 4 in the order of the test program whilst no coin is present The amplitudes of the signals in the appropriate coils are measured in turn and their values are stored. If at any time these amplitudes vary within preset limits the appropriate stored values are updated.

When a coin 6 is deposited in the passage 8 it will immediately cause a change in the measurements outside the preset limits and this change is recognised and used to initiate the test program for the coin. As soon as the presence of a coin is detected the test program is stopped and after a predetermined delay is recommenced with the first test. The delay is long enough to ensure that the coin is correctly positioned.

The circuit then subjects the coin to each of the test, signals in the order of the test program. For each signal in turn the amplitude is measured at the appropriate coil and the ratio of the measured amplitude with the coin present to the corresponding stored amplitude measured without a coin present is formed by the converter 1 8. This ratio is compared with the corresponding reference value stored for a first acceptable coin. If it is equivalent within preset limits, the next test test is initiated. If there is no equivalence, the ratio is compared successively with the corresponding reference values stored for other acceptable coins.

Once the ratio is found to be equivalent to one of the corresponding reference values stored the other tests are initiated in order. During the further tests the amplitude ratio formed in each case is compared with the corresponding reference value stored for the coin identified during the first test.

Accordingly, if the coin is validated by all the tests its value has also been identified.

If, the amplitude ratio formed by the first test is not equivalent to any of the reference values stored for the first test the control unit 1 6 generates a reject signal and the coin is passed into the coin reject channel 1 3. If during the following tests, any amplitude ratio is not equivalent to the corresponding reference value stored in respect of the coin identified by the first test it is compared with the corresponding reference values for other acceptable coins. This enables the system to discriminate between coins of different values which have some parameters in common. Of course, if the coin being tested does not produce a set of amplitude ratios which which are each equivalent to the corresponding reference value stored for a single acceptable coin, the coin in the passage 8 is passed into the coin reject channel 13.

If the coin being tested is validated the control unit 1 6 generates an accept signal which operates the respective flap 7 to enable the coin to pass into the accept channel 12. At the same time, the control unit 1 6 recycles the circuit such that the test signals are once more applied to the coils 4 to continue the "no coin" measurements until a further coin is deposited. Not only does this reset the system such that it is ready to receive the next coin but it also enables the system to ensure that the validated coin has been passed to the accept channel 12. Thus, if the amplitude measurements which are commenced do not agree with the stored values the system recognises that a coin is still in the passage 8. The coin may have jammed, or may be on a string to prevent it falling into the accept channel 12. in this case, the control unit 16 generates a reject signal. If the recommencement of the test program shows that no coin is present in the passage 8 the value of the coin validated is entered in the output register 20.

As it is the ratio of two amplitudes which is compared with the reference value stored it will be appreciated that the validation of the coin is independent of any variations in the amplitude of the test signals.

It will be apparent to anyone skilled in the art that the sequence in which the steps of the test program are performed may be varied from that described above in accordance with the program used and the facilities offered by the logic circuits employed.

Claims

1. A method of examining coins comprising the steps of holding a coin to be examined at a predetermined position, and subjecting the coin held at said predetermined position to at least one oscillating electromagnetic signal to produce an output indicative of the effect of the coin on the or each electromagnetic signal.

2. A method as claimed in Claim 1, in which the coin is subjected to a number of electromagnetic signals having different frequencies such that different parameters of the coin are examined.

3. A method as claimed in Claim 1 or 2, in which the coin is subjected to an electromagnetic signal having a frequency greater than or equal to 100KHz.

4. A method as claimed in any preceding claim, in which the coin is subjected to an electromagnetic signal having a frequency in the range 1 Hz to 75 KHz.

5. A method as claimed in any preceding claim, in which the coin is subjected to a first electromagnetic signal having a frequency in the range 1 to 75 KHz and to a second electromagnetic signal having a frequency in the range 1 Hz to 1 KHz.

6. A method as claimed in Claim 5, in which the frequency of the first signal is 7.812 KHz and the frequency of the second signal is 1 22 Hz.

7. A method as claimed in any preceding claim, in which the or each oscillating electromagnetic signal is generated by energizing one or more inductive coils positioned near said predetermined position.

8. A method as claimed in Claim 7, in which the or each inductive coil is energised at different frequencies simultaneously.

9. A method as claimed in Claim 7, in which the or each inductive coil is energised at different frequencies consecutively.

10. A method as claimed in any preceding claim, in which the coin is held at said predetermined position against a profile arranged such that one or more dimensions of the coin determine the spacing of said coin from a first inductive coil.

1 A method as claimed in Claim 10, in which the profile is stepped and/or curved and the coin is arranged to rest against the profile when the coin is held at said predetermined position.

12. A method as claimed in Claim 10 or 1 in which said first inductive coil has a diameter which is smaller than the diameter of the smallest of the acceptable coins.

13. A method as claimed in any of Claims 1 to 9, in which the coin is held at said predetermined position adjacent a first inductive coil having a diameter greater than that of the coin to be examined.

14. A method of determining one or more dimensions of a coin comprising the steps of holding the coin against a profile arranged such that the dimensions of the coin determine the spacing of said coin from a first inductive coil, energising said first inductive coil at a predetermined frequency to subject the coin to an oscillating electromagnetic signal at said predetermined frequency such that the effect of the coin on said electromagnetic signal is indicative of the spacing of the coin from the first inductive coil

1 5. A method as claimed in Claim 14, in which the first inductive coil is spaced from a second inductive coil to define a passage therebetween in which said predetermined position is as least partially located.

1 6. A method of validating coins comprising examining a coin as claimed in any preceding claim and comparing the or each output indicative of the effect of the coin with the or each electromagnetic signal with stored reference values.

17. A method as claimed in Claim 16, in which the or each oscillating electromagnetic signal is generated by energising one or more inductive coils positioned near said predetermined position, and in which one inductive coil is energised at a first frequency when no coin is held at said predetermined position and the amplitude of the oscillating electromagnetic signal generated by said coil is detected, said one inductive coil is energised at said first frequency when a coin to be validated is held at said predetermined position and the amplitude of the oscillating electromagnetic signal generated by the coil is detected, and the ratio of said two amplitudes is compared with a reference value.

1 8. A method as claimed in Claim 17, in which a range of reference values associated with said first frequency is stored for comparison with said ratio.

1 9. A method as claimed in Claim 17 or 18, in which each coin is subjected to a number of oscillating electromagnetic signals at different frequencies either consecutively and/or simultaneously.

20. A method as claimed in any of Claims 1 7 to 19, in which with no coin at said predetermined position the inductive coil is cyclically energised at a number of predetermined frequencies and that the amplitude of the oscillating electromagnetic signal at each frequency is measured and stored.

21. Apparatus for examining coins comprising means for holding a coin to be examined at a predetermined position, and means for subjecting the coin held at said predetermined position to at least one oscillating electromagnetic signal.

22. Apparatus as claimed in Claim 21 comprising a coin chute having a passage defined between two inductive coils energisable to generate the or each electromagnetic signal, and stop means for arresting a coin at said predetermined position within the passage.

23. Apparatus as claimed in Claim 22, comprising a shaped profile located within the passage, and wherein said stop means are arranged to arrest a coin deposited in the chute such that the coin rests against the profile.

24. Apparatus as claimed in Claim 23, wherein the profile is arranged such that the thickness and/or diameter of the coin determines the spacing of the coin from one of said inductive coils.

25. Apparatus as claimed in any of Claims 22 to 24, further comprising a control and measurement circuit arranged to generate signals for energising one or both of said inductive coils and for detecting an output indicative of the parameters of the coin.

26. Apparatus as claimed in Claim 25, wherein the control and measurement circuit is electronic and is arranged to measure said output and/or compare said output with a preset reference.

27. Apparatus as claimed in Claim 25 or 26, wherein the control and measurement circuit further includes means for actuating the stop means to release the coin once the examination thereof has been completed.

28. A coin deposit chute for a coin validation system, the chute comprising a passage for receiving a coin defined between two inductive coils, a shaped profile located within said passage, and stop means for holding a coin deposited in said chute against the profile, wherein the profile is shaped such that the thickness and/or diameter of the coin determines the spacing of the coin from one of said inductive coils.

29. A coin deposit chute as claimed in Claim 28, wherein said stop means comprises first and second solenoid operated stop members, the first stop member being operable to direct the coin held against the profile into a first channel and the second stop member being operable to direct the coin held against the profile into a second channel.

30. A coin validation system incorporating a coin deposit chute as claimed in Claim 28 or 29, and further comprising an electronic control and measurement circuit for energising one or both of the inductive coils and detecting the effect of a coin held against the profile on the signals generated by the coils

31. A method of examining and/or validating coins substantially as hereinbefore defined with reference to the accompanying drawings.

32. A method of determining one or more dimensions of a coin substantially as hereinbefore defined with reference to the accompanying drawings.

33. Apparatus for examining and/or validating coins substantially as hereinbefore defined with reference to and as illustrated in the accompanying drawings.

34. A coin deposit chute for a coin validation system substantially as hereinbefore defined with reference to and as illustrated in the accompanying drawings.