Control circuit
BACKGROUND OF THE INVENTION 
     The present invention relates to a circuit device for effecting and memorising adjustments to the setting of the controls of a television signal receiver, especially of a colour television receiver; such controls as the volume, brightness, contrast, colour saturation etc. must often be adjusted when changing stations in order to obtain optimum setting of the controls for each station to which the receiver can be tuned in order to account for differences in the signals from each station. Conventionally, television controls are mechanical control systems using potentiometers inserted into the path of the electric signal to be controlled (direct control) or else supplying a D.C. voltage by means of which electronic voltage control is effected (indirect control). 
     Such mechanical systems have considerable disadvantages, not only from the point of view of durability, since the potentiometers, being mechanical, are subject to wear, but also from that of performance due to non-linearity and discontinuity in the response. Moreover, such mechanical systems are not easily adaptable to the use of remote controls. 
     For this reason wholly electronic control systems, which operate indirectly, have been recently introduced. These usually comprise a series of counters which are able to count both up and down, each followed by a suitable digital-to-analogue converter. By energising a counter, selected by operation of one of a number of pairs of push buttons, it is possible to increase or reduce the content of this counter and thereby to cause the corresponding control voltage to vary: such variation is discontinuous, but has sufficient resolution for most purposes. 
     This latter system eliminates many of the disadvantages of the conventional mechanical controls but it is still not wholly satisfactory because, since each station to which a receiver can be tuned usually has modulation characteristics which are different from those of the others, with every change of station it is necessary to readjust, systematically, the controls of the receiver, that is the volume, brightness, contrast (and colour controls in the case of colour transmission). 
     In fact at present it is possible in many places to receive a large number of transmitter stations (in some cases more than twenty), and hence television receivers have to allow changeover from one station to another with the greatest simplicity. The technical problem which this invention seeks to solve is the provision of a circuit device which is able to effect adjustment of the controls of a receiver upon changes in the tuning thereof to receive signals from different transmitters, which does not suffer from the disadvantages of known systems. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided a circuit device for carrying out and memorising adjustments to the tuning of a television receiver for a plurality of transmitter stations, of the type having memory means for memorising the value of control signals determining the tuning of the receiver, in which the said memory means are also operable to produce an output signal characteristic of the station to which the receiver is tuned, and there are means for feeding this signal as an address signal to further memory means in which are stored signals determining the adjustment to at least one of the controls of the receiver, other than the tuning control, means for effecting adjustment of this control automatically in dependence on the said stored signals when the tuning of the receiver is changed to select a different station, and means for selectively changing the signal stored at any one address in the said further memory means whereby to change the adjustment to the said one control of the television receiver. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Two embodiments of the invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 is a schematic electrical diagram of an adjustment and memorisation circuit for the controls of a television receiver, constructed and arranged as a first embodiment of the present invention; 
     FIG. 2 is a schematic electrical diagram of a second embodiment of the present invention, which is somewhat simpler than the circuit shown in FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1 of the drawings there is shown a control panel 1 which is provided with six adjustment buttons or keys 2, 3, 4, 5, 6, 7. The buttons or keys 2, 4, 6, are connected each to a first input of respective OR gates 8, 9, 10, to respective inputs of a six input OR gate 11, and each to an UP/DOWN input (which controls the counting direction) of a respective one of three counters 16, 17 and 18. The buttons 3, 5, 7 are connected, respectively, to the second inputs of the OR gates 8, 9, 10 and to the remaining three inputs of the OR gate 11. 
     The output of the OR gate 11 is connected to a first input of an AND gate 12 and, through a differentiator circuit comprising a capacitor 13 which is earthed via a resistance 14, to the reset inputs (R) of the three counters 16, 17, 18; the second input of the AND gate 12 is fed with a signal from a clock generator 15, and the output of the AND gate 12 is connected to the clock inputs (CP) of the three counters 16, 17, 18. The outputs of the three counters 16, 17, 18 are connected, selectively by means of respective switch circuits 19, 20, 21, to the input/output terminals of three random access memories 22, 23, 24 and at the same time to the inputs of three digital-to-analogue converters 25, 26, 27 and, also at the same time to the preset inputs (PS) of the said three counters 16, 17, 18. The outputs of the three OR gates 8, 9, 10, are connected via respective delay circuits 28, 29, 30, to the &#34;enable&#34; inputs (CE) of respective switch circuits 19, 20, 21 and at the same time to the read-write (R/W) inputs of the random access memories 22, 23, 24. Address signals are fed to the three RAMs 22, 23, 24 from a terminal N fed from the output of a tuning control memory 49 having also an input/output line fed from a processor circuit 48 which receives control signals from a tuning control panel 47 having a plurality of push buttons or keys 47a selectively operable to choose the station to which the receiver is to be tuned. The terminal N line of the memory 49 also feeds a tuning control circuit 50 incorporating a digital-to-analogue converter and operating in a known way to control tuning of the receiver in dependence on the station selected. This system operates in a known way and does not form part of the inventive concept of the present invention, and therefore will not be further described. 
     The outputs of the digital-to-analogue converters 25, 26, 27, indicated by V, L and S, supply the adjustment voltages for the volume, brightness and colour controls. 
     The circuit described above operates as follows: 
     When any receivable transmitter station is selected by operation of the station selector panel 47 of the television receiver, there is applied to the input N, by the memory 49 associated therewith, a binary signal representing the selected transmitter station: this binary signal addresses the three random access memories 22, 23, 24 so that at the output thereof there is reproduced the information at present stored in those cells of the memories associated with that transmitter station, which represents the levels of the adjustment signals which were selected on a previous occasion when the receiver was tuned to that transmitter station. 
     The pairs of buttons 2, 3; 4, 5; and 6, 7 may be used to adjust any three of the controls of the receiver: in this example the controls to be adjusted thereby are the volume, brightness and colour saturation respectively, although they may be connected to control contrast or fine tuning of the receiver instead. The buttons 2, 4 and 6 select adjustment of the associated control in one direction, for example increasing volume, increasing brightness and increasing colour saturation, and the buttons 3, 5 and 7 select adjustment in the opposite direction, decreasing the volume, brightness or colour saturation respectively. 
     Upon depression, for example, of the key 2 a rest impulse is applied, through the gate 11 and the differentiator circuit comprising the capacitor 13 and resistor 14, to each of the three counters 16, 17, 18 which are then predisposed to count, starting from respective numbers which are preset, at the PS inputs thereof, from the outputs of the respective memories 22, 23, 24. The output signal from the gate 11 also enables the gate 12 to pass the clock pulses, generated by the generator 15, to the clock inputs of the three counters. 
     Depression of the key 2 also feeds a signal to the OR gate 8 which thus provides an output signal which, after a time delay T introduced by the delay circuit 28, sets the memory 22 to the write mode and opens the switch circuit 19 to pass on signals received from the counter 16 to the memory 22, which records them. The counters 16, 17 and 18 are predisposed to count DOWN and depression of the key 2 passes a signal to the U/D input of the counter 16 to set this in the count UP mode. When the counter 16 receives the preset signal from the RAM 22 it then starts to count up, and this is recorded simultaneously, in that cell of the memory 22 at the address, corresponding to the selected station, determined by the address signal on the input N, and the D/A converter 25 therefore supplies an increasing voltage which causes the volume to increase until the key 2 is released. During this operation, since none of the keys 4, 5, 6 or 7 have been depressed, the gates 9 and 10 have given no signal, and the content of the memories 23 and 24 has not changed. 
     Upon depressing the key 3, operation of the circuit is identical to that described above, except that no signal is fed to the U/D input of the counter 16 and hence the counter stays set to count down; there is thus produced a reduction in the content of the RAM 22 at the selected address with a corresponding reduction of the output voltage V, and hence a reduction in the volume of the receiver until the key 3 is released. 
     The pairs of keys 4, 5 and 6, 7 operate in exactly the same way to control, respectively, the counters 17 and 18 and thus the content of the memories 23 and 24. In the absence of any adjusting control effected by depression of the keys of the control panel 1 the digital-to-analogue converters 25, 26, 27 are fed with signals representing the content of the random access memories at the addresses determined by the signal at the input N and the receiver controls remain set at values determined by these. 
     In the embodiment of FIG. 2, components fulfilling the same function as corresponding components in the embodiment of FIG. 1 are indicated with the same reference numerals. 
     The UP keys 2, 4 and 6 of the control panel 1 are connected to respective inputs of an OR gate 42, the output of which is connected to a first input of another OR gate 43 and to the counting direction control input (U/D) of a counter 37; the DOWN keys 3, 5 and 7 are connected to respective inputs of an OR gate 41, the output of which is fed to a second input of the OR gate 43 the output of which is connected to an input of the gate 12 and to the capacitor 13 of the differentiator circuit including the earthed resistor 14. 
     The output of the OR gates 8, 9, 10 are connected to the enabling inputs (C.E.) of respective switching circuits 19, 20, 21, and via respective delay circuits 44, 45, 46, to the read-write inputs (R/W) of respective random access memories 22, 23, 24 and to respective inputs of an OR gate 47 the output of which is fed to the enable input (CE) of a switching circuit 38. 
     The clock input of the counter 37 is connected to the output of the gate 12, the reset input is connected to the capacitor 13, the preset input is connected to the three switching circuits 19, 21, 21, and the output is connected to the input of the switching circuit 38 the output of which is fed back to the preset input of the counter 37 and is connected to the three switching circuits 19, 20, 21. 
     The circuit described with reference to FIG. 2 operates as follows: 
     By depressing one of the keys 2, 4 or 6 the counter 37 is preset, via the gate 42, to count upwards, and via the gate 43 the passage of clock signals through the gate 12 is enabled. At the same time the associated one of the gates 8, 9 or 10 produces an output signal which enables the associated one of the switching circuits 19, 20 or 21 to pass signals fed to it. The output signal from the said one of the gates 8, 9 or 10, after a delay T introduced by the associated delay circuit 44, 45 or 46 is fed to the read/write input of the associated one of the random access memories which is thereby set to write; at the same, delayed, time the switching circuit 38 is enabled. 
     Meanwhile the signal from the gate 43 has supplied a reset impulse to the counter 37 which then starts to count, from the preset content of the memory 22, 23 or 24, when this arrives. 
     As in the embodiment of FIG. 1, the content of the memory 22, 23 or 24, at the address determined by the signal at the input N is altered, and hence the corresponding output voltage increases, and continues to increase until the key is released. 
     By pressing the keys 3, 5 or 7 the same operation is produced, but without energisation of the U/D input of the counter which thus counts down from the number preset by the content of the associated RAM at the selected address, whereby to reduce the controlled parameter. 
     The counters 16, 17, 18 of FIG. 1, and the counter 37 of FIG. 2 are all identical with each other and are of the six bit output type. Likewise the memories 22, 23 and 24 and the converters 25, 26, 27 are also of the six bit type. Moreover the above mentioned counters are so constructed and arranged that counting ceases as soon as a maximum value of 63 or a minimum value of 0 is reached. 
     From the above description the advantages of the device of the present invention will be clearly appreciated. By operation of this circuit it is possible to associated, with every transmitter station which can be received by a receiver, the selected best setting of the receiver controls, so that it is not necessary to readjust the controls upon each change of station in order to obtain optimum reception. Moreover it is very simple, if necessary, to alter the previous adjustments for any given station should reception conditions change, and the new values will automatically be memorised and used each time the receiver is tuned to that station unless and until the adjusted values are again changed. 
     Naturally, in order to retain the information when the receiver is switched off the memories 22, 23, 24 have to be of the non-volatile type, or else of the low consumption type (MOS) in order thay they may be supplied by a separate voltage source, such as a dry cell, when the main voltage source is disconnected. 
     Many variations are possible without nevertheless going beyond the scope of the present invention. For example, the control board need not be directly connected to the rest of the circuit as shown in the above examples, but may be connected by a remote control system, for example using infra red rays; moreover the circuit may be modified so that the counters are caused to move gradually at each pressure from a control key or button so that greater precision of adjustment is obtained. Likewise, although the RAM memories 22, 23, 24 and the tuning memory 47 are shown as independent memories, they may be formed as parts of a single common memory device.