A coin discriminator comprises photoreceivers along a vertical drawn from an infed coin run chute whereby screening and illuminating the photoreceivers from a photoemissive source permit coin diameter identification. Two coils on either side of the chute detect the coin alloy. Coin thickness is determined using a stepshaped transversal section across the chute track where the step risers lie opposite the photoreceivers which transmit a signal word identifying the infed coin diameter and thickness. This signal word is compared with memorized words representative of acceptable coin dimensions. If the dimensions are acceptable, a combination of impedances in a bridge circuit incorporating the coils is selected in terms of the alloy corresponding to the acceptable dimensions. If the bridge balances for this combination as the coin rolls between the coils, the coin is accepted.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a multicoin (multitoken) discriminator comprising 
a chute having a vertically inclined track on which infed coins (tokens) 
roll. The coin discriminator is intended for an automatic object or 
service vending machine. 
2. Description of the Prior Art 
Multicoin discriminators as described in French patent applications 
2,461,987 and 2,466,055 comprise coin dimension recognizing means in the 
form of two electromagnetic field producing coils on either side of the 
coin roll-in chute. The diameters of the coils are such that the upper tip 
of a coin having a minimum acceptable diameter enters only a small portion 
of the coil electromagnetic field; a coin having the maximum acceptable 
diameter enters the entire electromagnetic field. One of the coils, 
referred to as an oscillating coil, is connected to an oscillating circuit 
which delivers a high frequency signal, typically 100 kHz. The other coil, 
a so-called receiving coil, transmits a voltage to voltage comparison 
means; the voltage is proportional to the magnetic flux intensity through 
which the upper part of each coin passes. Reference voltages 
representative of the diameters of varying acceptable coin types are 
compared with the voltage transmitted by the receiving coil to deduce 
whether the coin should be accepted; if the coin is acceptable it has a 
diameter between the minimum and maximum diameters; otherwise the coin is 
refused. 
In the foregoing patent applications, the coin alloy detecting means make 
use of the same voltage comparison principle. 
Another coin discriminator, disclosed in French patent application 
2,448,752, selects only one type of coin, i.e., admits only coins having a 
predetermined diameter and made of a predetermined alloy or material. 
The principle behind the means for recognizing alloys resides in the 
description hereinabove. The alloy recognizing means also comprises two 
coils disposed opposite each other. One of the coils is excited by an a.c. 
generator. A signal induced in the other coil has an amplitude that is 
compared with a predetermined voltage to determine if the coin between the 
coils is acceptable; if the amplitude is less than the predetermined 
voltage the coin is acceptable. 
The coin dimension recognizing means taught in French patent application 
2,448,752 comprises two light sources and phototransistor light detecting 
pairs. The light detectors are spaced from each other by a distance 
virtually equal to the acceptable coin type diameter. Should one or both 
the phototransistors be excited, the infed coin does not have the required 
diameter and is rejected. 
Known previous discriminators thus adopt coin diameter and alloy as the 
sole selection criteria. An infed coin having the acceptable diameter and 
alloy is therefore accepted regardless of thickness. This offers a further 
non-negligible opportunity of fraudulently introducing improper coins or 
slugs into the vending machine. Moreover, the diameter recognizing means 
taught in French patent application 2,466,055 permits acceptance of coins 
having diameters that vary over only a relatively small range. If the 
vending machine is to accept coins having many different diameters, the 
measurement device for distinguishing between the diameters require high 
sensitivity and very precise setting; the number of voltage comparing 
circuits equals the number of different diameters. The alloy recognizing 
means also requires a number of voltage comparing circuits equal to the 
number of denominations to be detected. 
OBJECTS OF THE INVENTION 
The main object of this invention is to provide a multicoin discriminator 
which discriminates infed coins in terms of the coin thickness. 
Another object of this invention is to provide a multicoin discriminator 
which discriminates the infed coins in terms of the coin diameter, 
thickness and alloy. 
A further object of this invention is to provide a multicoin discriminator 
in which the dimension recognizing means and the alloy recognizing means 
are unique and utilized for all coin types. 
SUMMARY OF THE INVENTION 
To discriminate coins in terms of diameter and thickness, a multicoin 
discriminator in accordance with one embodiment of the invention, 
comprises photoemission means lodged in one of the side walls of the coin 
chute for selectively illuminating photoreceptive means lodged on the 
other side wall of the chute and in front of the photoemissive means for 
detecting the dimensions of the infed coins. A stair-shaped transversal 
cross-section between the photoemissive means and photoreceptive means 
positioned in the bottom of the chute has its lowest step or platform 
adjacent an inclined side wall of the chute against which one face of the 
coins rests. 
The photoreceptive means can comprise several charge transfer devices (CTD) 
or several phototransistors aligned respectively opposite to risers of the 
stair-shaped transversal cross-section and likely to capture the 
preferable infrared rays emitted by the photoemissive means. 
The stair cross-section in the track provides thickness differentiation 
regarding the acceptable coins. By screening the photosensitive receivers 
opposite the risers and other photosensitive receivers above the step, a 
binary word is produced which identifies the diameter thickness of each 
acceptable type of coin. Recognition of acceptable dimensions is achieved 
by means connected to the photosensitive receivers for detecting a 
diameter and thickness identification word for each coin fed into the 
chute, a memory having memorized words respectively identifying the 
acceptable coin dimensions and means for comparing each detected word with 
the memorized words in order to accept or reject the infed coin. 
According to another aspect of the invention, the stepshaped transversal 
cross-section is replaced by an inclined plane cross-section making a 
predetermined acute angle with the inclined side wall of the chute. 
To discriminate coins in terms of alloy, a multicoin discriminator 
comprises two series-connected coils on opposite sides of said chute for 
detecting the alloy of each infed coin, oscillator means having a 
predetermined-frequency, and means for memorizing words representating the 
alloys of acceptable coins. Two combinations of parallel impedances are 
respectively addressable by all said memorized words for each infed coin. 
An impedance bridge means excited by said oscillator means has four arms, 
one of which includes the two series-connected coils. Two adjacent arms 
respectively include the two parallel impedance combinations. A bridge 
means balance detection means compares the detected alloy of each infed 
coin with all said alloys representated by said memorized words to accept 
or reject said infed coin. 
According to other aspects of the invention, a complete multicoin 
discriminator embodying the invention comprises the above diameter and 
thickness discriminating means and the above alloy discriminating means. 
One of these two discriminating means can accept an infed coin after the 
other has detected and validated the infed coin in terms of the diameter 
and thickness, and the alloy. 
Other features, advantages and objects of this invention will be more 
clearly apparent from the following description of preferred exemplified 
embodiments as illustrated in the accompanying corresponding drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Schematically depicted in FIG. 1 is a discriminator for coins or tokens 
presenting different diameters, thickness and alloys. The discriminator 
includes coin C dimension recognizing means 1--2 and coin C alloy 
recognizng means 3--4. Each of these means comprises a coin detecting 
device 1, 3 that is located along chute 5 for the coin C gravity infed run 
and a circuit 2, 4 associated with respective detecting device 1, 3 for 
comparing the detected dimensions or alloy with the pre-recorded values 
therefor. Circuits 2 and 4 are included in a logic control unit 6 which, 
from the comparison results, determines whether an infed coin is to be 
accepted and honored or rejected and reimbursed. 
The multicoin discriminator is located in a known object or service vending 
machine. Mention is made henceforth solely of those means in this machine 
directly related to the multicoin discriminator. 
As shown in FIG. 1, run chute 5 has an input 50 having a single slot into 
which the coins are fed, and a double output 51--52. The double output 
consists of a first output 51 for acceptable coins that fall into a 
collection box in the vending machine and a second output 52 for the 
rejected coins above the vending machine reimbursement receptacle. The 
chute output selection between the accepted and rejected coins is obtained 
by means of an electromagnet 60 that is controlled by unit 6 through a 
wire 61. Electromagnet 60 holds the bottom of the run chute open by means 
of a retractable hatch 62 until such time as the relative dimension or 
alloy comparisons are no longer negative. 
Run chute 5 generally has a rectangular cross-section and descends along a 
track 53 from input 50 down to output 51--52. In the illustrated 
embodiment, starting from input 50, a coin first crosses dimension 
detecting device 1 and then crosses alloy detecting device 3. 
In reference now to FIGS. 2 and 4, the width of chute track 53 is equal to 
the largest acceptable coin thickness. Track plane 53e at the input 50 end 
is a higher level than plane 53a of the track running from device 3 down 
to output 51--52. Between parallel planes 53e and 53a that have the same 
direction if inclination, the track is formed as a staircase having plural 
risers and platforms (steps) in cross-section at right angles to the 
rolling direction of coin C as illustrated in FIG. 4. The stepped section 
is illustrated as comprising three intermediate steps 54b, 54c, and 54d, 
located between lower step 54a and upper step 54e. Steps 54a and 54e are 
coplanar with the track planes 53a and 53e respectively. 
Moreover, longitudinal side walls 550 and 551 of chute 5 are rearwardly 
inclined such that gravity causes all the coins to rest on lower wall 550. 
As shown in FIG. 3, the longitudinal transitions or risers between plane 
53e that is an extension of upper step 54e, and following step 54d, 
between steps 54d and 54c, between steps 54c and 54b and between step 54b 
and lower plane 53a that is an extension of step 54a, are respectively 
formed of rectangular inclined planes 56d, 56c, 56b and 56a. These 
inclined planes adjoin wall 550 against which one of the coin faces rests 
by gravity. Downstream of device 1 and upstream of device 3, the chute 
further comprises inclined planes 57d and 57a which form respective 
transitions between steps 54e to 54a; planes 57a-57d are adjacent upper 
longitudinal wall 551. As can be seen in FIG. 3, steps 54e to 53a between 
walls 551 and 550 form longitudinal parallel strips, each off-set with 
respect to the previous one down to the output. 
The inclined planes provide a progressive descent for coins with differing 
thickness between upper plane 53e and lower plane 53a of the track. It 
goes without saying that other configurations and longitudinal lay-outs of 
the inclined planes may be envisioned. 
Generally speaking, each stair in the staircase has a different height and 
width. 
The distances between rear support wall 550 and the risers and other wall 
551 are slightly greater than the five different acceptable coin 
thickness. For example, as depicted in FIG. 5, a thin coin C.sub.a rolls 
from the upper track plane 53e successively over inclined planes 56d to 
56a and along lower step 54a whereas a coin C.sub.e having a thickness 
greater than the distance between wall 550 and the upper riser and equal 
at the most to the width of chute 5, runs firstly over upper step 54e and 
then over inclined planes 57d to 57a. 
Semiconductor photosensitive receivers 10a to 10i respond to light energy 
from source 11, as blocked by token or coin C, as it rolls through device 
1 to enable the coin thicknesses and diameters to be detected. The length 
of a region of receivers 10a to 10i that is not illuminated determines the 
token diameter. The length of a zone of receivers 10a to 10i between 
lowest step 54a and the lowest edge of token C that is illuminated 
indicates the coin thickness; the coin thickness is detected only while 
the coin diameter is detected. 
With reference to FIGS. 2 to 6, dimension detecting device 1 comprises a 
photoemissive source 11 and a plurality of photosensitive receivers 10a to 
10i such as phototransistors. Photoemissive source 11 may emit optical 
energy in the visible band, but preferably is an infrared emitter to 
obviate any parasitic detection of light that might stem from coin input 
slot 50. Photoemissive source 11 includes either a lamp or a 
light-emitting diode (LED) or several photoemissive diodes. The 
photosensitive receivers can be replaced by any other electro-optical 
means such as charge transfer device (CTD) or camera, e.g. a bar of 
charged coupled devices (CCD) described in detail hereinafter. 
Photoemissive source 11 is fixed behind a slit 12 in upper side wall 551 
of the chute and is perpendicular to chute track 53 and thus to all steps 
54e to 54a. Phototransistors 10a to 10i are inserted in support wall 550 
where they are also aligned with the vertical from track 53 in the 
transversal plane that is perpendicular to walls 550 and 551 and median to 
slit 12. The transversal plane follows line IV--IV in FIGS. 2 and 3 and 
lies in line with a step transversal section of track 53. Slit 12 can be 
replaced by holes formed in chute upper wall 551. One hole is provided for 
each of transistors 10a to 10i, so each is aligned with the vertical from 
chute track 53 and positioned opposite the phototransistor associated with 
it. 
As illustrated in FIG. 6, lower phototransistors 10a to 10d are 
respectively positioned opposite the centers of the straight risers. In 
the drawing, phototransistors 10e to 10i are equally spaced between upper 
step 54e and the upper edge of wall 550. However, in practice, the number 
of phototransistors 10a to 10i can be greater and the phototransistors can 
be spaced from each other by distances associated with the various 
acceptable coin diameters. Last phototransistor 10i is usually slightly 
higher than the highest acceptable coin rolling down the step section in 
order to detect any improper coins or slugs having an excessive diameter. 
As a result, depending on phototransistor screening and excitation, circuit 
2 in logic unit 6 can deduce the diameter and thickness of a coin. When 
photoemissive source 11 excites a lower phototransistor 10a to 10d, the 
thickness of the coin is greater than the distance between support wall 
550 and the corresponding riser. Between the highest excited lower 
phototransistor 10a to 10d and the lowest excited phototransistor, the 
other phototransistors are screened to indicate the coin diameter. 
Three examples of coins to be detected are given in FIGS. 7 to 9. The high 
logic signals a to i indicate the respective excitation of 
phototransistors 10a to 10i whilst complementary logic signals a to i 
indicate the respective screening of phototransistors 10a to 10i. 
As seen in FIG. 7, the width of an infed coin C.sub.c lies between the 
distances separating wall 550 from the risers of steps 54c and 54d. Coin 
C.sub.c therefore rolls along step 54c. The diameter of coin C.sub.c is 
slightly greater than the distance between phototransistors 10c and 10g. 
As a result, phototransistors 10c to 10g are screened and phototransistors 
10a, 10b, 10h and 10i are excited by source 11. In this case, a bus 13 
connected to the phototransistors delivers the detected word a b c d e f g 
h i to circuit 2. 
Referring now to FIG. 8, the infed coin C.sub.b rolling along second step 
54b has a diameter slightly greater than the distance between 
phototransistors 10b and 10h. The word detected and delivered along bus 13 
is a b c d e f g h i. 
In FIG. 9, the coin W has the same dimensions as in FIG. 8, but has a hole 
drilled through the center thus forming a washer. The central hole of coin 
W enables radiation from source 11 to be incident on and excite 
phototransistor 10e, thus causing the word transmitted on bus 13 to be a b 
c d e f g h i. Consequently, when circuit 2 recognizes at least two 
separate signal groups at the lower level in the logic signal derived by 
detectors 10a-10i, it deduces that the infed coin has a hole through it; 
the coin is thus unacceptable and must be rejected by retracting hatch 62 
controlled by eject electromagnet 60. 
Should a buckled coin become jammed, means (not shown) can be provided for 
ejecting the coin manually or electromechanically into the reimbursement 
receptacle by off-setting at least chute support wall 550. 
Each acceptable coin is characterized by a word identifying the coin 
diameter and the thickness. In the embodiment illustrated in FIG. 10, 
dimension comparing circuit 2 comprises a read-only memory (ROM) 20 having 
predetermined addresses containing nine-bit words respectively identifying 
the dimensions of all coin types the vending machine is supposed to 
accept. The memory 20 is preferably reprogrammable (REPROM) thus allowing 
the company managing the machine to select the acceptable coins in terms 
of the service or object vending cost. 
Circuit 2 further comprises, in the embodiment illustrated, a buffer shift 
register 21 with at least nine stages, a time base 22, a read addressing 
circuit 23 for read-only memory 20 and a logic comparing circuit 24 having 
input buses 240, 241 connected to the parallel outputs of memory 20 and 
register 21. Bus 13 transmits the parallel bits of the dimension 
identifying binary words to time base 22. 
Time base 22 periodically reads the words in bus 13 and includes means for 
successively comparing these words two by two in order to select and 
retain only that word having the greatest number of bits with the low 
logic level between two predetermined instants closely corresponding to a 
coin passing between slit 12 and phototransistors 10a to 10i. The selected 
word corresponds to the diametral section of the coin passing through the 
chute. Time base 22 then orders the following cycle. 
The selected identification word is recorded in buffer register 21 via a 
bus 220. Next, via a lead 221, the time base simultaneously controls the 
reading of register 21 and the reading of a first acceptable coin 
dimension identifying word in memory 20 to addressing circuit 23. 
Comparing circuit 24 transmits the comparison result via output lead 242 
thereof to time base 22. Until such time as the comparison result is no 
longer negative, the time base orders other acceptable coin identifying 
words memorized in read-only memory 20 to be read in order to compare them 
with the word detected and recorded in register 21. 
Should no comparison be positive, time base 22 sends orders via wire 61 for 
the infed coin to be rejected by opening hatch 62. For a positive 
comparison, the memory 20 reading cycle is halted and an address is 
transmitted via bus 200 from memory 20 to an alloy memory 40 incorporated 
in alloy comparing circuit 4. Each coin dimension identifying word stored 
in memory 20 is stored with an address word from memory 40 which 
characterizes the alloy of that coin having acceptable dimensions 
corresponding to the identification word that is detected in the time base 
22 and stored in the register 21 of circuit 2. 
When the multicoin discriminator embodiment does not comprise device 3 and 
circuit 4, the address words for memory 40 go unused. 
According to another embodiment illustrated in FIGS. 4A and 4B, the 
photoreceptive receiving means included in the dimension detecting device 
1 includes a charge coupled device (CCD) bar. The N cells 14.sub.1 to 
14.sub.N of the CCD bar replace the phototransistors 10a to 10i. In 
practice, the integer N is higher than the number of phototransistors 
because of the integrated structure of the bar. The vertical definition 
with a CCD bar may reach at least a tenth of a millimeter. The CCD bar is 
lodged in the support side wall 550 and is perpendicular to the track 53 
of the run chute 5 and opposite the slit 12. 
As shown in FIGS. 4A and 4B, the steps 54a and 54d are replaced by an 
inclined plane 58 making a predetermined acute angle .alpha. with respect 
to the lower support wall 550. When an infed coin C rolls down chute 5, 
gravity causes one of its faces to rest against wall 550; the edge of its 
opposite face rolls on inclined plane 58 that is provided between upper 
track 53e and lower track 53a. As previously, the screened CCD cells, such 
as above cell 14.sub.3 for a thin coin C.sub.f having a thickness 
.DELTA.t.sub.f (FIG. 4A), or above cell 14.sub.5 for a thick coin C.sub.g 
having a thickness .DELTA.t.sub.g (FIG. 4B), give the diameter of the 
coin. The excited lower cells, such as cells 14.sub.1 and 14.sub.2 for 
coin C.sub.f or cells 14.sub.1 to 14.sub.4 for coin C.sub.g, directly 
define the thickness .DELTA.t of the coin according to the formula: 
EQU .DELTA.t=.DELTA.l.multidot.t.sub.g .alpha. 
where .DELTA.l is the distance between the lower portion of the coin and 
the apex of angle .alpha., i.e. the length along which the lower cells are 
excited. Preferably, .alpha. is equal to .pi./4 to simplify the 
calculation since .DELTA.t=.DELTA.l for this case. 
The dimension comparing circuit according to this embodiment enables the 
coin diameter to be determined, as above mentioned. The dimension 
comparing circuit further enables the coin thickness to be directly 
determined in terms of the formula .DELTA.t=.DELTA.l by comparing the word 
that is delivered from the lower excited CCD cells, with a memorized 
thickness identifying word for the corresponding diameter of an acceptable 
coin. 
The multicoin discriminator according to this embodiment is suitable for 
all the acceptable coin types without mechanical modifications; on the 
contrary, the width of each step according to the first embodiment 
corresponds to a predetermined coin thickness. These modifications are 
only obtained by programming the acceptable coin thickness and diameter 
table that is stored in the reprogrammable memory (REPROM) in the circuit 
2. 
In reference now to FIG. 11, a description follows of alloy recognizing 
means 3-4. 
Alloy detecting device 3 comprises, as is known, two electromagnetically 
coupled coaxial coils 30 and 31 opposite one another. Coils 30 and 31 are 
respectively inserted in longitudinal side walls 550 and 551 of run chute 
5 above lower plane 53a. The common axis of coils 30 and 31 is 
perpendicular to walls 550 and 551 and preferably lies in line with the 
average center of the coins rolling along plane 53a, in line, for example, 
with that of upper step 54e. 
Beside the already mentioned alloy identifying word memory 40, circuit 4 
comprises a Wheatstone bridge circuit 41, an amplifying circuit 42, an 
integrating circuit 43 and a threshold comparing circuit 44. 
Terminal 410, common to two adjacent arms in impedance bridge circuit 41, 
is connected via input resistor 421 to direct input 420.sub.+ of an 
operational amplifier 420 that is included in amplifying circuit 42. Each 
of these two arms has a plurality of parallel-connected circuits 451-461 
to 454-464, 455-465 to 458-468, numbering in this four, for instance. Each 
of these circuits comprises a complex impedance 451 to 458 (that may be 
adjustable) and an analog switching circuit 461 to 468 of the 
relay-controlled contact type, resistor type or the RCA CD4066 "analog 
switch" type for example. The first of the foregoing arms (the upper one 
in FIG. 11) comprises, in series with four parallel-connected circuits 
451-461 to 454-464, two series-connected coils 30 and 31 together with a 
complex impedance 411 that may include a thermistor. The second foregoing 
arm (the lower one in FIG. 11) comprises two impedances 413 and 414 that 
are respectively and preferably resistive and capacitive and are connected 
in series with the other four parallel-connected circuits 455-465 to 
458-468. 
Applied to the other terminals 415-416 of the foregoing arms of bridge 
circuit 41 is the voltage from a.c. generator 417 having a 
predetermined-frequency suitable for discriminating between coin alloys. 
Between terminals 415 and 416 are the third and fourth arms Wheatstone 
bridge circuit 41, respectively comprising impedances 418 and 419, that 
are preferably resistive and capacitive and are connected to ground. 
In analog amplifying circuit 42, inverse input terminal 420.sub.- of 
amplifier 420 is connected to grounded resistor 422, and a feedback 
resistor 423 that is connected to output 424 of amplifier 420. 
Integrated circuit 43 comprises two resistors 430 and 431 having a common 
terminal connected to a grounded capacitor 432. The other terminal of 
resistor 431 is connected to one of inputs of the voltage comparator 411 
which is included in circuit 44. 
Threshold comparing circuit 44, between the positive supply terminal and 
ground, further includes a resistor 442 and a potentiometer 443, having a 
common terminal connected to a resistor 444. The other terminal of 
resistor 444 is connected to a common terminal of grounded capacitor 445 
and input 446 of comparator 441. The output of comparator 441 is connected 
via controlling wire 61 to electromagnet 60 for ejecting refused coins. 
Potentiometer 443 is set such that the voltage across comparator terminal 
446 is equal to the bridge circuit 41 balance voltage applied to terminal 
440 via circuits 42 and 43. 
Each group of analog switches 461 to 464, 465 to 468 is controlled by a 
4-lead output bus 401, 402 from alloy identifying word memory 40. Prior to 
any utilization of the device, adjustable impedances 451 to 458 are set 
such that for certain open and closed combinations of switches 461 to 468, 
i.e. predetermined impedance 451 to 458 combinations, each of the alloys 
or materials characterizing all the acceptable coins introduced between 
coils 30 and 31 indicates the bridge circuit balance status; the bridge 
balance status is indicated by a high logic level output signal on wire 
61. An alloy identifying word in reprogrammable read-only memory 40 
(REPROM) corresponds to each switch open/close or impedance combination 
for each predetermined alloy. 
Subsequent to time base 22 (FIG. 10) enabling the diameter and thickness 
dimension for an infed coin in response to recognition of a dimension 
identifying word transmitted along bus 13 and stored in memory 20, memory 
20 delivers to bus 200 the alloy identifying word address that is 
memorized in the memory 40 and which corresponds to the alloy of an 
acceptable coin with the detected dimensions; bus 200 is supplied with the 
alloy word after a lapse of time corresponding to the time the coin takes 
to run between devices 1 and 3. Switches 461 to 468 are controlled via 
buses 401 and 402 and positioned to enable the corresponding alloy to be 
detected. If the infed coin causes bridge circuit 41 to be balanced upon 
running between coils 30 and 31, comparator 441 activates ejection 
electromagnet 60 (FIG. 1) to close hatch 62 over which the coin rolls 
towards the output 51 and the collection box. In the opposite case, if the 
coin has the appropriate dimensions, but bridge 41 is not balanced since 
the coin composition does not correspond to the required alloy for such 
dimensions, the low level signal on wire 61 holds hatch 62 open and the 
coin is returned to the user. 
In the embodiment wherein the multicoin discriminator comprises only means 
for recognizing alloys 3-4, circuit 4 fulfills functions analogous to 
circuit 2. In this case, circuit 4 comprises a time base 22 which 
successively readouts addresses of the alloy identifying words in memory 
40 until the time base detects a low level signal at the output of 
comparator 441; the low level output enables the infed coin. 
Alternatively, if the output of comparator 441 indicates no balance of 
bridge circuit 41 for all the close/open combinations of analog switches 
461 to 468 stored in memory 40, hatch 62 stays open to reject the 
unacceptable coin. 
In a further embodiment, alloy detecting device 3 can be located upstream 
of dimension detecting device 1 along the chute 5 coin track. In this 
case, the relative control functions of circuits 2 and 4 are reversed. 
Circuit 4 comprises a time base 22 which cyclically reads memory 40 until 
bridge circuit 41 is detected as balanced. In response to this balance, 
memory 40 addresses memory 20 so comparator 24 can compare the word on bus 
13 with that addressed in memory 20. As previously, if the bridge circuit 
is balanced and if, for this balance, the comparison result in comparator 
24 is positive, hatch 62 is activated to close the chute track. 
Lastly, in a more integrated embodiment, dimension recognizing circuit 2 is 
structured around a microprocessor 25, as shown in FIG. 12. The 
microprocessor 25 comprises a random access memory (RAM) that is utilized 
for successive two-by-two comparisons of the words coupled to bus 13 as 
the coin rolls through the chute. Circuit 2 further comprises a 
reprogrammable memory 26 and an input/output interface 27. Pre-recorded in 
memory 26 are the acceptable coin dimension identifying words and the 
orders corresponding to the comparison cycle, as described herein with 
reference to FIG. 10. Circuits 25, 26 and 27 are interconnected 
conventionally via a unidirectional bus 28 for the addresses leaving 
microprocessor 25 and via a bidirectional bus 29 for the orders and data. 
Interface 27 is linked to bus 13, connected to photoemissive means 10a to 
10i (FIG. 5) or 14.sub.1 to 14.sub.N (FIGS. 4A and 4B); bus 200, serving 
alloy identifying word memory 40 (FIG. 11), controls wire 61 of 
electromagnet 60 that controls retractable hatch 62 (FIG. 1), and 
directly, in this case, to respond to the output of voltage comparator 44 
(FIG. 11). Bus 270 can connect interface 27 to other equipment, such as a 
display means. In this microprocessor embodiment, memory 40 (FIG. 11) can 
also take the form of a microprocessor.