Price display setting arrangements

A unit price setting arrangement for differently priced products available from a remotely located dispenser for example, grades of fuel, from a pump, consists of a central transmitter and a receiver in each dispenser. The transmitter forms a series of fixed length binary words, one for each product, and transmits them in sequence repetitively. Each receiver counts words of the sequence received and compares them with the position of a selected product in the sequence to determine which word relates to the product of interest. That word only is used and is applied to a comparator with a corresponding word stored from a previous transmission to detect a change in the word. A shift register having a stored bit responds to an unsuccessful comparison to shift the bit through one location and a shift through a predetermined number of locations by successive unsuccessful comparisons, if the change is permanent, causes a controller to replace the stored value with the newly received one. The shift register is reset by a correct comparison if the change indicated by the comparison is not sustained and the stored value is unaltered. Thus any disturbance giving rise to a wrong binary word is ineffective but a deliberate change repeated over several transmissions is effective.

This invention relates to price setting arrangements and in particular to 
such setting arrangements for remotely controlled apparatus at which any 
one of a number of products, each of which may have a price different from 
the others, may be selected. 
One example of such remotely controlled apparatus is for dispensing liquid 
fuel, such as petrol, at so-called "self-service" sites where a plurality 
of dispensers, or pumps, under the control of a central supervisor are 
arranged to be operated by customers who select the grade of fuel required 
and dispense it themselves. Measurement of the fuel dispensed and 
calculation of the cost incurred is performed in the dispenser by 
apparatus monitored by the supervisor. Such apparatus and the control 
thereof is described fully in our co-pending application No. 35883/75. 
Whereas in operation the cost of a delivery, calculated from data generated 
by the dispenser, is both transmitted to the central apparatus and 
displayed to the customer, it is necessary to generate within each 
dispenser for display to the customer the unit price charged for each 
product prior to operation of the dispenser. This has been done in the 
past by having switching means relating to all possible prices connected 
to the grade selector switch whereby as each grade is selected the unit 
price for that grade is determined by the switching means is displayed on 
that particular dispenser. Where a large number of grade selections is 
possible then a large number of individual switches are required in the 
switching means. Furthermore, when a price change occurs, the supervisor 
or some other person has to set all of the switches to reflect the new 
unit price for each grade. This setting has to be carried out for each 
dispenser on the site, during which operation of the station must be 
suspended to avoid different dispensers indicating different charge rates. 
It is an object of the present invention to provide a central unit price 
setting arrangement for remotely controlled apparatus at which any one of 
a number of products, each having a price which may be different from the 
others, may be selected. 
According to the present invention a price setting arrangement for remotely 
controlled dispensing apparatus from which any one of a number of products 
may be selected has a transmitting unit. This unit is located separately 
from the remotely controlled apparatus and is operable to transmit a 
signal repetitively to the apparatus. The signal includes the unit prices 
of all the products. A receiving unit is carried by the remotely 
controlled apparatus and includes recognition means responsive to the 
selection of a particular product to recognise the unit price signal 
transmitted in respect of that product. Comparison means is used to 
compare the recognised received price signal in each transmission with a 
signal stored from a previous transmission together with circuitry 
responsive to a predetermined successive number of comparisons made 
without identity between the received price signal and the stored signal 
to replace the stored signal by the received price signal. 
The transmitting unit may comprise manually settable switches operable to 
produce for each unit price a unique binary word of fixed length and a 
scanner operable to produce the binary word representing each unit price 
in turn and to transmit the binary words in a sequence. 
The switches may comprise a shift register having a plurality of parallel 
loading inputs corresponding to the number of bits of the fixed length 
word. A switching matrix comprising a plurality of input lines, one for 
each product is employed with a plurality of output lines. Each output 
line is connected to individual inputs of the shift register, the input 
and output lines being connectable by individually closable switches. Thus 
when any input line is energised, selected output lines, joined by closed 
switches, apply a signal to associated shift register inputs to produce a 
serial binary word which can be clocked out of the shift register output. 
The scanning means may comprise a divider circuit responsive to clock 
pulses applied to the shift register to divide the clock frequency by the 
number of bits in each fixed length word. The divided signal is applied to 
the shift register to load into the shift register the word appearing at 
the input terminals thereof after the previous one has been clocked out 
serially. A further counter is responsive to the divided signal to 
energise each input line of the switching matrix in turn to provide a new 
word for the shift register each time it is loaded. 
The transmitting unit may include further switches operable to produce a 
control word serving to identify the start of transmission and to transmit 
the control word followed by said unit price identifying words. 
In the measuring unit the recognition structure may comprise to provide a 
product code signal representing the number of the product selected in the 
sequence in which the unit price identifying words are generated. A timer 
provides a number which increases by one in synchronism with each word 
transmitted. A comparator is operable to compare the two signals and 
provide a recognition signal when the word number of the sequence thereof, 
corresponds to the product selected. 
The transmitting unit may also include a monitor receiving unit operable to 
simulate selection of any one of the products selectable at the remotely 
controlled apparatus. The receiving unit is arranged to receive signals 
transmitted and to display the unit price of the product whose selection 
is simulated.

The principle of operation of the invention as applied to dispensing motor 
fuel will be described before the circuit in order to help in 
understanding of the latter. The remotely controlled unit is one of 
several self-service fuel pumps subject to a central control. Each pump is 
able to deliver up to eight grades of fuel, the grade for delivery being 
selected by the customer at the start of the operation. 
When a grade is selected it is necessary to display to the customer the 
unit price to be charged for that grade of fuel. 
To this end a transmitter unit at the central location generates and 
transmits repetitively to all pumps a binary signal comprising nine words 
each of twenty bits length. The first word is a control word and contains 
identity and control information. It serves to transmit a code identifying 
the start of a transmission sequence, correct reception of which code is 
required to permit subsequent operation. Part of the word may contain 
control information for the pump, for example, switching between 
self-service and operator control and/or to introduce a scaling factor, 
such as changing the position of a decimal point. The subsequent eight 
words are each related to the unit price of an individual grade of fuel 
and are transmitted in succession after the control word. The control word 
is in two parts, each of ten bits length, an initial 1 followed by nine 
0's defining the start of the sequence after which each fifth bit is a 1. 
Thus the second part of the first word has two groups of four bits which 
may contain control information. 
Of the subsequent twenty-bit words each fifth bit is again a 1 so that no 
confusion can arise between them and the control word, the other sixteen 
bits being available to contain information. 
The signal is transmitted under the control of clock pulses so that each 
word lasts for twenty clock cycles and the whole signal is repeated every 
180 cycles of the clock. 
The receivers in the pumps are identical and each receives each control and 
price identifying word in the order of transmission, that is, for grades 
one to eight. The grade selection switch functions to identify grades 
selected in the same order as they occur in transmission. Say the selector 
switch is set to grade five, then after the control word is received the 
number of words received are counted until the fifth is received and it is 
only this word which is recognised and acted upon. The received word is 
passed to a comparator with a stored previously received word. The stored 
word is continuously displayed. If the comparison is positive, that is, 
there is identity, the unit price is assumed unchanged and the stored 
value retained. If the comparison is negative, that is, there is 
non-identity, a signal is produced and if several, say three, successive 
negative results are achieved the unit price is assumed to have changed 
and the word newly received is shifted into the store to represent the new 
unit price. In this way random occasional disturbances of the signal are 
ineffective in changing the stored word but a consistent change due to a 
modified transmitted signal does effect such a change. 
In order to implement the operating scheme the unit price transmitter shown 
in FIG. 1 comprises a clock pulse generator 11, operation of which may be 
inhibited by a detector circuit 12, connected to a circuit input terminal 
13 and through which externally generated clock pulses may be supplied. 
The output line 14 of the clock is connected to a divide-by-twenty circuit 
15, the output of which is connected to a counter 16. The counter 16 has 
nine output terminals and is arranged to produce an output at each in turn 
in a repetitive cycle. A switching unit 17 comprises a shift register 18 
and a switching matrix 19. The shift register 18 has twenty parallel input 
terminals P1-P20 and a serial output terminal 21. The register is loaded, 
that is a binary word formed by signals appearing on the input terminals 
P1 to P20 is entered into the register, when a signal from the divider 15 
is applied to a "load" terminal 22, and the word is clocked out serially 
by clock pulses from line 14 applied to terminal 23. 
In accordance with the desired formats of transmitted words, inputs P1, P11 
and P16 are connected to a positive supply rail as is P6, except when the 
control word is generated, so that every fifth bit is normally a 1. The 
other inputs P2-P5, P7-P10, P12-P15, P17-P20 are connected to the 
switching matrix. 
The switching matrix comprises nine input lines (or rows) R1-R9 connected 
one each to a corresponding output of the counter 16 and sixteen output 
lines (or columns) C1-C16 connected one each to a corresponding input of 
the shift register 18. 
The line R1 is connected to input P6 by way of an inverting amplifier and 
the input is normally energised like P1, P11, and P16 when R1 is 
de-energised but is de-energised i.e. becomes a `0`, when R1 is energised 
so that the first ten bits of the control word are automatically generated 
in the shift register 18. The line R1 is also connected to lines C9 and 
C10 by switch S1 and to lines C11 and C12 by switch S2 so that by 
operation of S1 and S2 the second part of the word can be used to transmit 
control instructions which will be described in detail later. 
All of the remaining lines R2-R9 are connected to lines C1-C16 at the 
intersections between sets of lines by way of switches shown symbolically 
at S3 and each including an isolating diode (not shown). 
The price of each grade is entered by closing selected switches on each 
line representing a particular grade to produce a binary equivalent of the 
price. 
To consider performance of the transmission operation with reference to the 
circuit described, clock pulses are generated at 400 Hz producing 
word-loading pulses at 20 Hz. At each word-loading pulse a different line 
Rn of the switching matrix is energised and the appropriately energised 
lines C1-C16 apply inputs to the shift register 18 in addition to the 
fixed inputs. The word-loading pulse causes the word to be loaded into the 
shift register where it is clocked out of output 21 serially by the next 
twenty clock pulses before the next word-loading pulse is generated. Nine 
words are generated in turn and transmitted continuously from an output 
amplifier 24 on line 26. 
At the same time clock pulses are transmitted continuously by way of an 
amplifier 25 on line 27. 
The receiver located in each pump is shown schematically by the block 
diagram of FIG. 2. The grade selector switch 30 of the pump produces a 
product code signal in the form of binary number 1 to 8, according to the 
selection, on lines 31 applied to one input of a binary comparator 32. A 
receiver 33 accepts the 400 Hz clock signal on line 27 from amplifier 25 
and feeds an output to a resettable divide-by-twenty circuit 34. The 
divider circuit 34 feeds pulses to a counter 35 which provides a different 
binary output for each pulse until reset. The binary outputs are fed to 
the other input of the comparator 32 which provides an output when there 
is identity between the binary signals. In operation the divide-by-twenty 
circuit 34 and counter 35 are reset by a signal produced as hereinafter 
described when the control word is received. Counter 35 thus produces an 
increasing output for each subsequent word received by the pump and when 
the word representing the selected grade is received the comparator 32 
provides a recognition signal. This part of the receiver comprises a 
recognition means. 
The transmitted signal is applied on line 26 to a shift register 37 which 
provides each twenty-bit word at parallel outputs indicated by 38. A 
gating arrangement 39 receives the first 10 bits entered into the shift 
register and if the word consists of "1" followed by nine "0"s the gate 
passes a reset signal on line 40 to the divide-by-twenty circuit 34 and 
counter 35 of the recognition means. 
The parallel outputs of the register 38 are fed also to corresponding 
inputs of a store 41 and of a comparator 42. The output terminals of the 
store are fed to display devices by way of terminals 43 and to the other 
inputs of the comparator 42. The comparator is arranged to provide an 
output signal to a shift register 44 when there is no identity between the 
signals applied. The store 41, comparator 42, and shift register 44 are 
all operated under the control of recognition signals applied to their 
clock inputs by the output of comparator 32 so that operation takes place 
once in each transmission for the received word representative of the 
selected grade but for no other. 
Each time the word corresponding to the selected grade is received that 
word is fed to the comparator 42 with the stored word 41, which stored 
word is also fed to the display to indicate the unit price of the selected 
grade. 
If the comparison is true, that is, the received word is identical with the 
stored word, the comparator gives an output to a shift register 44 to 
reset it to zero. 
If the comparison is not true, that is, there is non-identity, a shift 
signal is fed to the shift register 44. If three successive untrue 
comparisons are made the shift register 44 gives an output signal to a 
control circuit 45. This applies a "load" signal to the store 41 to 
replace the previously stored value with the currently received one. 
The signal may be used to control the pump motors using lines 50 and 51, if 
desired, such that a deliberate price change when the pump is in operation 
causes discharge to terminate until a new operation, at new price, is 
commenced. 
Initially the store 41 will be empty which means that after switch-on the 
first three comparisons are untrue and on the third transmission cycle the 
unit price value of the selected grade is entered into the store for 
display. With a clock frequency of 400 Hz and a message time of 180 clock 
cycles the display is visible after less than two seconds. Similarly where 
there is a deliberate grade reselection, or unit price change, the new 
unit price becomes visible in less than two seconds. In the particular 
application of petrol pumps this delay between change and display is 
acceptable. On the other hand if noise interferes with the transmission 
such that the selected price word is interfered with, by having a bit 
change in one or more locations, for one or two transmissions the 
comparator 42 gives an output signal but because the change is not 
maintained the shift register 44 does not give an output signal to change 
the stored unit price value. 
Earlier it was mentioned that only part of the first word of each 
transmission was required to identify the start of a sequence. The outputs 
of register 37 corresponding to this part of the word are fed to gate 39 
as hereinbefore described. Some of the remaining outputs of register 37 
comprise a sub-word or sub-words and are fed to a further store 46, 
similar to store 41, and to a parallel comparator 47, similar to 
comparator 42. Comparator 47 is also connected to the shift register 44 to 
reset it when a successful comparison is made and store 46 feeds two 
output terminals 48 and 49.In the example illustrated by FIG. 1 two 
subwords are characterized by the states of switches S1 and S2 
respectively in the transmitter and the terminals 48 and 49 are present 
signals representing those of sub-words. The sub-words defined by the 
position of switch S1 serves to indicate the position of a decimal point 
in the display of unit price, effectively providing a .times.10 scaling 
factor. The sub-word represented by switch S2 is recognized in 
conventional manner by a control circuit (not shown) which determines 
whether the pump is to be operated in a self-service mode for example by 
preventing unauthorized removal of the dispenser nozzle. It will be 
understood that the sub-words received may be used to operate subsidiary 
display parts and/or initiate control functions to be undertaken by 
subsidiary control parts of the dispenser. 
Whereas the store 41 and comparator 42 are triggered once per transmission 
upon recognition of the appropriate price word by signals from the 
comparator 32, the store 46 and comparator 47 are triggered once per 
transmission by correct reception of the first part of control word, by a 
signal on line 40. 
Where each dispenser is employed as one of many under the supervision of an 
operator or cashier at the central location the transmitting unit may 
include a monitor receiving unit containing a grade selection switch 30 
and display unit so that the operator can select any one of the grades to 
verify that the correct unit price is being transmitted for the grade 
selected. 
The price setting arrangements is not of course limited to use with petrol 
pumps or the dispensing of fuel. It may be employed with only minor 
changes to other forms of dispenser of other products.