according to the most preferred aspect of the invention , an orientation strip with identification zones which are assigned to the control elements and have haptically coded surfaces is arranged on the control surface . such an orientation strip may be provided instead of , or in addition to , haptically coded control elements . such an orientation strip makes it possible to determine , even before the control element is actually touched , toward which control element the finger is moving . since the push - button keys or rotary knobs themselves do not need to have haptic coding when such an orientation strip is present , identical keys may optionally be used at different points of the control unit so that the diversity of parts is somewhat reduced . it is particularly expedient that the orientation strip extends underneath the respective control elements , preferably along the lower edge of the control surface . this edge area of the control unit is accessed extremely easily by the fingertips and is in an ergonomically convenient position . the fingertips contain a particularly large density of touch receptors so that this area is particularly sensitive . in order to distinguish individual identification zones or groups of identification zones more easily , it is proposed to provide delimitation structures or means between the identification zones or groups of identification zones . these delimitation structures or means are preferably formed by webs which are slightly elevated and run essentially transversely with respect to the longitudinal direction of the orientation strip . the webs which are only slightly elevated above the surface of the identification zones do not impede the feeling of the identification zones in any way and , on the other hand , the delimitation which can be felt clearly makes assignment easier . it is also possible to arrange the push - button keys in the identification zones , as a result of which space is saved and the controllability made easier . in order to code the surfaces on the control elements or identification zones , a characteristic structure , for example , by means of roughness , a pattern or direction of a pattern , may preferably be provided . a further measure for coding the surfaces is to generate on the surfaces of neighboring push - button keys or identification zones a temperature which feels significantly different to the skin . this can be effected for example with the aid of a peltier element . according to a first embodiment of the invention , the control elements have a haptically coded surface . as a result , the control element itself is identified individually . expediently , at least some of the control elements of a control unit are constructed as push - button keys with characteristic front surfaces . such front surface structures can be realized without appreciable additional outlay when the push - button keys are manufactured . for different reasons , for example , design or ergonomy , it may be necessary to construct one or more control elements as a rotary knob . so that the rotary knob can also be distinguished haptically in terms of the various functions to be set , the rotary knob is constructed with at least a partially coded part of its surface . so that the set operating function of a control element can also be made apparent in a visual way , it is advantageous to assign to one or more control elements a display , in which the function which has been set is displayed . for the functions which can be adjusted infinitely or in a plurality of stages , it is considered expedient to assign two neighboring push - button keys with adjustment in opposite directions to the same function , i . e ., one key is used to increase the value of the respective function , and the other key to reduce the value . in order to code in a suitable way these push - button keys located one next to the other , it is considered advantageous that the front surface of one push - button key is provided with a concave depression and the front surface of the other push - button key is provided with a convex bulge . push - button keys which are designed in this way are particularly suitable as desired - value actuators for adjusting the temperature , and a display which serves as a digital temperature display is assigned to these push - button keys . in vehicles with higher demands on the heating and air conditioning comfort , the air which flows into the passenger compartment should be capable of being adjusted individually to suit the respective driver and front seat passenger . for this purpose it is expedient to provide two arrays of push - button keys and a temperature display for adjusting the temperature in the control unit , one array serving to adjust the heating or air conditioning requirement for the driver &# 39 ; s side and the other array serving to adjust it for the front seat passenger &# 39 ; s side . in order to provide a clear differentiation between the push - button keys assigned to the front seat passenger &# 39 ; s side and the push - button keys assigned to the driver &# 39 ; s side , it is advantageous for the control surface to be divided into two control areas , each control area forming essentially a plane and the two planes being arranged at an angle with respect to one another . by means of such a division of the control surface into control areas , it is also possible to make a division according to other criteria , for example , into an area with control elements which serve to promote traffic safety ( defrosting of the windshield , heating of the rear window ) and control elements for personal comfort ( temperature of the passenger compartment , blower power , air distribution ). by means of such an arrangement of planes which enclose an angle , it is expedient to arrange the control area with the control elements which are particularly relevant to the driver in such a way that the surface of the control panel runs as far as possible perpendicularly with respect to the driver &# 39 ; s line of sight . to this end , the contact line between the two planes should run essentially vertically and the angle between the front sides of the planes should be approximately 185 ° to 200 °. in the case of a control surface which runs obliquely with respect to the plane of the dashboard , it is advantageous for the orientation strip to form -- in plan view -- at least in an essential section of its longitudinal extent , a wedge - shaped surface which is deeper on one side than on the other side . as a result , identification zones of different sizes are produced so that simply the size of the identification zones serves as an additional feature for making a haptic distinction . for ergonomic reasons , it is expedient to arrange the orientation strip at an angle with respect to the control surface , with an angle of approximately 100 ° to 140 ° between the control surface and the orientation strip being considered particularly expedient . in order to inform the driver of the setting which he has made , a device for audible acknowledgment of a setting of one of the control elements can also be advantageously provided . referring now to the drawings , fig1 shows a control unit 1 which has a control surface 3 on one housing 2 . the face of the control surface 3 which serves for visual purposes should be arranged perpendicularly with respect to the driver &# 39 ; s line of sight . the control surface is divided into two control areas 4 and 5 , the control area 4 being assigned to the driver and the control area 5 being assigned to the front seat passenger . the control areas 4 and 5 are arranged in planes which run at an angle with respect to one another , with the plane of the control area 5 running parallel to the plane of the dashboard . the control area 4 faces the driver as a result of its arrangement at an angle with respect to the control area 5 , so that the driver &# 39 ; s view is directed as far as possible perpendicularly onto the control area 4 of the control surface 3 . the control area 4 comprises a display 7 for displaying a temperature . this display 7 is assigned to two push - button keys 8 and 9 which serve as desired - value actuators for the desired passenger compartment temperature on the driver &# 39 ; s side . in this context , the push - button key 8 is provided for increasing the desired value and the push - button key 9 for reducing the desired value . furthermore , in the control area 4 of the control surface 3 there is a display 10 which extends above a push - button key for defrosting the windshield and a push - button key 12 for heating the rear window . the display 10 comprises a display 13 with the letters def and a display 14 with the letters hs which each appear only in the switched - on state of the respective push - button key 11 or 12 . a display 17 for displaying a desired value of the temperature of the passenger compartment of the vehicle on the front seat passenger &# 39 ; s side and push - button keys 18 and 19 are arranged in the control area 5 of the control surface 3 . these push - button keys correspond to the push - button keys 8 and 9 and fulfill the same function : however , they are for adjusting the desired value of the temperature for the front seat passenger &# 39 ; s side . an orientation strip 15 extends along the lower edge of the control surface 3 on the housing 2 , and comprises a plurality of identification zones 20 , 21 , 22 , 23 and 20 &# 39 ;, 21 &# 39 ; each assigned to one push - button key . these identification zones each have a surface with a characteristic structure so that when a finger of the operator touches an identification zone it is possible to determine which of the push - button keys 8 , 9 , 11 , 12 and 18 , 19 the finger is located in front of , i . e ., on the basis of the quality of the surface of the respective identification zone . in this way , the respective push - button keys can be distinguished haptically so that precise assignment is possible with certainty even without visual support . in the exemplary embodiment in fig1 crosses which stand out in a relief - like manner on the surface of the identification zone 20 are provided as plus symbols , corresponding to the function of the associated push - button key . the surface of the identification zone 21 is provided with short , transversely running bars which are raised in a relief - like manner and characterize a minus sign . owing to the substantially larger number of relief - like elevations in the identification zones 21 in comparison with those in the identification zone 20 , it is possible to make a haptic distinction even if the shape of the relief - like crosses ( plus signs ) cannot be perceived unambiguously . the identification zone 22 has ribbing with pointed elevations arranged in rows . on the surface of the identification zone 23 there is a plurality of dot - shaped knobs ; however , a roughened surface could also be provided instead . owing to the structures of the identification zones 20 to 23 which differ from one another significantly , it is possible to locate with certainty the respective identification zone by means of the sensitivity of the skin , e . g . tickling , vibration , sensation of heat and of cold , on the basis of its coded surface . the push - button keys 18 and 19 are assigned identification zones 20 &# 39 ;, 21 &# 39 ; on the orientation strip 15 , the surface structure corresponding in each case to the identification zones 20 , 21 . since the orientation strip 15 forms in the plan view , at least over an essential section of its longitudinal extent , a wedge - shaped surface which is deeper on one side than on the other side , the identification zones 20 and 21 are significantly larger than the identification zones 20 &# 39 ;, 21 &# 39 ;, so that a difference between the zones 20 and 20 &# 39 ; can also be felt . of course , the control surface 3 may also comprise further push - button keys and , if appropriate , also switches for additional functions , for example , for fresh air or circulating air mode . fig2 shows the front view of a control unit 30 which comprises a housing 31 and a plurality of displays 33 , 34 , 35 arranged on a control surface 32 , and push - button keys 36 , 37 , 38 , 39 and 36 &# 39 ;, 37 &# 39 ;. the control surface 32 comprises in turn the control areas 4 and 5 similar to those already described with respect to fig1 . underneath the control areas 4 and 5 extends an orientation strip 15 of the same general type as detailed in conjunction with fig1 . ( therefore , the orientation strip is not shown in detail in fig2 .) the displays 33 , 34 , 35 are of different design from the embodiment previously described , as are the push - button keys 36 to 39 , but they serve the same purpose in accordance with their arrangement . in contrast with the embodiment already described , in the exemplary embodiment of fig2 the push - button keys 37 to 39 are provided on their front surfaces with a characteristic structure so that when the push - button keys 37 to 39 are touched it is possible to make a distinction haptically . these haptically coded surfaces are shown in the illustration in fig3 in which there is a section along the line iii -- iii in fig2 . this illustration also shows that the control areas 4 and 5 of the control surface 3 are arranged at an angle α with respect to one another , a contact line 6 being formed at the point of intersection of the two planes . the angle α is 185 ° in the exemplary embodiment but an angle α of up to about 200 ° may equally well be provided . the front surfaces of the push - button keys 36 to 39 are provided with haptic coding so that the push - button keys themselves can be distinguished haptically , in other words , independently of the orientation strip . the push - button key 36 for increasing the desired value for the passenger compartment temperature on the driver &# 39 ; s side has a convex bulge 40 , and the push - button key 36 &# 39 ;, which has the same function for the passenger compartment temperature of the front seat passenger &# 39 ; s side , has the same shape . the push - button key 37 serves to reduce the desired value for the passenger compartment temperature and has a convex depression 41 on its front surface ; the push - button key 37 &# 39 ; in the control area 5 has the same shape . the push - button key 38 for defrosting the windshield is provided on its front surface with a burled structure 42 . a burled pattern with pointed knobs is provided on the front surface of the push - button key 39 for heating the rear window . thus , all the push - button keys 37 to 39 which are assigned to the control area 4 differ as a result of the structure of their front surface , which structure can be located with certainty without visual aid . the fact that the push - button keys 36 &# 39 ;, 37 &# 39 ; have the same characteristic front surface as the push - button keys 36 and 37 in the control area 4 does not lead to them being confused since the push - button keys with identical front surfaces are assigned to different control areas 4 and 5 . fig4 shows a section along the line iv -- iv of fig2 . in the housing 31 of the control unit 30 there is , set back somewhat with respect to the front edge , the control surface 32 with the control areas 4 and 5 . the display 33 and the push - button key 37 with its concave depression 41 located on the front side are arranged in the control area 4 . a surface 44 which drops away obliquely with respect to the front edge of the housing 31 and facilitates the guidance of the finger of the operator towards the push - button keys extends along the lower edge of the control surface 32 . this surface 44 is designed as an orientation surface with identification zones as already described with respect to fig1 . it is thus perfectly possible to provide the push - button keys 36 to 39 with a haptically coded front surface and to arrange in addition an orientation strip with identification zones . in this context , the surfaces of the identification zones should have the same structure as the respective push - button key to which the identification zone is assigned . the angle β of the oblique surface 44 with respect to the control surface 32 is approximately 105 ° in the exemplary embodiment , but depending on the embodiment of the control unit , this angle may be between 100 ° and 140 °. fig5 shows a control unit 50 in which a control surface 52 is formed on the front side of a housing 51 . the control surface 52 comprises a control area 53 and a control area 54 which are arranged in two planes running at an angle with respect to one another . a contact line 56 is formed between the control areas 53 and 54 . the control area 53 comprises a display 57 for displaying the desired value for the temperature of the passenger compartment of the vehicle . under the display 57 there are push - button keys 58 and 59 which respectively serve to increase and reduce the desired value . arranged next to the display 57 is a further display 60 which contains a display 64 for the currently set blower speed . underneath the display 60 there are push - button keys 62 and 63 which respectively serve to increase and reduce the blower speed . furthermore , the control area 53 comprises a display 61 with a display 65 of the air distribution which has been set . underneath the display 61 there are three push - button keys 66 , 67 , 68 by means of which the air distribution to footwell nozzles and to upper vents or a preferred basic position of the air distribution of all the vent nozzles can be set . the displays 57 , 64 , 61 and push - button keys 58 , 59 , 62 , 63 , 66 , 67 , 68 contained in the control area 53 serve to adjust the heating or air conditioning system according to the personal comfort of the driver . in the control area 54 there is a display 69 with two push - button keys 71 and 72 , the push - button key 71 being provided for defrosting the windshield and the push - button key 72 for heating the rear window . the operating state of the respective function is displayed on the display 69 . thus , the control area 54 comprises those push - button keys and displays of the functions relating to driving safety , namely a clear view through the windshield and through the rear window . an orientation strip 55 with wedge - shaped surface extends along the lower edge of the control area 53 , the orientation strip running as far as the contact line 56 of the two control areas 53 and 54 . each of the push - button keys 58 , 59 , 62 , 63 and 66 to 68 is assigned an identification zone 73 , 74 , 75 , 76 , 77 , 78 , 79 , these identification zones having a characteristically structured surface by means of which the respective push - button key can be identified haptically . in order to facilitate orientation , groups of identification zones are formed , between which delimitation structures or means are provided . these delimitation structures or means are formed by webs 70 which are slightly elevated and run essentially transversely with respect to the longitudinal direction of the orientation strip 55 . by means of these webs 70 , the identification zones 73 and 74 are thus combined to form a &# 34 ; temperature adjustment &# 34 ; group , the identification zones 75 and 76 are combined to form a &# 34 ; blower speed adjustment &# 34 ; group and the identification zones 77 to 79 are combined to form an &# 34 ; air distribution &# 34 ; group . the identification zone 73 is provided with relief - like minus signs and the identification zone 74 is provided with relief - like plus signs . the surfaces of the identification zones 75 and 76 are each provided with ribbing , the ribbing of the identification zone 75 running in the longitudinal direction of the orientation strip , and the ribbing of the identification zone 76 running transversely thereto . the identification zones 77 , 78 and 79 are provided with different knob patterns ; however , identification zones with a different degree of roughness could also be provided . the orientation strips 15 , 55 illustrated in the exemplary embodiments described above may be designed in such a way that a push - button key is arranged in each identification zone . as a result , the finger does not need to be moved from the identification zone to the push - button key , but instead , in order to generate a switching signal , pressure is exerted on the identification zone itself . furthermore , this saves space for the push - button keys underneath the displays so that the displays themselves can be larger in design , which serves to make them easier to read .