turn now to the drawings and initially to fig1 which illustrates a console 20 which may , for example , be a braille reader embodying the invention . a plurality of tactile display units 22 are embedded in an inclined upper surface 24 of the console 20 , so positioned that a blind person could readily read the information being presented at the same spacing as embossed braille text . each tactile display unit 22 is sized and shaped similar to a twelve pin dip ( dual in - line package ) ( see fig2 and 3 ) and is both mechanically mounted on the console 20 and connected electrically to its internal electronic circuitry in a manner not unlike a conventional integrated circuit ( ic ). data for display purposes on the console 20 are received from a host computer system ( not shown ) through an external interface 25 . turn now to fig4 - 7 , for a detailed description of the tactile display unit 22 . each unit 22 which is configured for a braille display includes a housing 26 formed with a plurality of cavities 28 , preferably cylindrical , generally arranged in two columns with three cavities per column . the central two cavities are slightly offset from the remaining or end cavities for a reason which will be explained subsequently . central axes of the cavities 28 are substantially parallel and are substantially equally spaced . as seen in fig5 a roof 30 is integral with the housing 26 , so positioned as to overlie all of the cavities 28 . the roof 30 defines a reference surface 32 which is preferably planar and has a plurality of apertures 34 suitably formed to enable communication between each cavity 28 and the reference surface 32 . a generally u - shaped electromagnet 36 is fixed to the housing 26 , as best seen in fig8 . it includes a central bight portion 38 , and a pair of upstanding legs 40 and 41 . the wall of the cavity 28 is formed with an elongated slot 42 which is generally parallel to the central axis of the cavity 28 . the leg 40 of the electromagnet 36 is fittingly received in the slot 42 . the slot is sufficiently deep that , when fully inserted , the bight 38 of the electromagnet 36 is spaced from an undersurface 44 of the housing 26 . this space permits fitting reception of a plug 46 which serves to seal the bottom of the cavity 28 . the outer surface of the plug 46 is substantially flush with the undersurface 44 . electrical leads 48 and 50 ( fig5 ) extend from opposite ends of the bight 38 through diametrically opposed openings 51 in the plug 46 and thereby define the legs 40 , 41 as being spaced poles of opposite , selectively reversible , polarity . the inner surface of the plug 46 is slotted , as at 47a , to accept the bight 38 of the electromagnet 36 and , together with the slot 42 , prevent any possible rotation of the electromagnet 36 within the cavity 28 . a generally disk - shaped cam 52 is positioned proximate to the electromagnet 36 , lying generally in a plane parallel to the bight 38 and extending between the legs 40 and 41 . the cam 52 is rotatable about an axis which is the same as that of the cavity 28 and perpendicular to the reference surface 32 . a permanent magnet 54 is suitably embedded in the cam 52 ( see fig9 ) and extends between spaced poles 56 and 58 of opposite polarity which are equidistant from the axis of rotation of the cam 52 . the cam 52 has a planar base surface 60 which is substantially parallel to the reference surface 32 and it has a contoured operative surface 62 on a side opposed to the base surface 60 which ranges between an elevated region 64 of maximum height above the base surface 60 and a nominal region 66 of minimum height above the base surface . a planar or wafer - like bearing member 68 ( see fig8 and 10 ) is desirably mounted on the bight of the electromagnet 36 . the bearing member 68 is preferably circular in shape with diametrically opposed notches 70 formed therein for engagement with the legs 40 and 41 to prevent relative movement between the bearing member and the electromagnet . a centrally positioned dimple 72 serves to freely receive a centrally disposed projection 74 which extends from the base surface 60 of the cam . the bearing member 68 is of a suitable material which enables substantially friction free rotation of the cam 52 thereon and , by reason of the interaction between the projection 74 and dimple 72 , serves to maintain the central positioning of the cam within the cavity 28 . also serving to maintain the position of the cam 52 within the cavity 28 is a positioning finger 76 which is integral with the housing 26 and extends downwardly from the roof 30 so as to be freely engageable with a centrally disposed depression 78 formed in the operative surface 62 of the cam . the term &# 34 ; freely engageable &# 34 ; is taken to mean that while the extreme tip of the positioning finger 76 is received within the depression 78 , it does not in fact bear against the cam during normal operation , but only if the cam tends to move off its axis as it rotates . in essence , then , the extreme tip of the finger 76 , the depression 78 , the projection 74 , and the dimple 72 all cooperate to serve as an axle to maintain the proper positioning of the cam on its axis of rotation and to transmit all of the magnetic force to that of rotation . also received within the cavity 28 is a touch pin 80 having a longitudinal axis which is substantially perpendicular to the reference surface 32 . the touch pin includes a follower end 82 which is engageable with the cam 52 and a tip end 84 distant from the follower end . the pin is movable on the cam 52 between a first position as seen at the left side of fig5 at which the tip end 84 is raised above the reference surface 32 and a second position as seen at the right side of fig5 in which the tip end 84 does not project beyond the reference surface when the cam is in an inactive position . that is , the cam 52 is in the active position with the follower end 82 is engaged with the elevated region 64 and is in the inactive position when the follower end is engaged with the nominal region 66 . intermediate the ends 82 and 84 , the touch pin 80 has an annular shoulder 86 which lies in a plane substantially perpendicular to the longitudinal axis thereof . a compression spring 88 encircles the pin and extends between the annular shoulder and the roof 30 and thereby biases the end 82 into engagement with the operative surface 62 of the cam . thus , when the electromagnet 36 is energized with a certain polarity such that the pole 56 of the permanent magnet 54 is caused to move to a position adjacent the leg 40 , the pole 58 is simultaneously positioned nearest the leg 41 and the cam 52 assumes its active position with the follower end 82 engaged with the elevated region 64 and tip end 84 projecting from the reference surface 32 ( left side of fig5 ). the elevated region may be provided with a slight recess 90 ( see fig8 ) to hold the follower end 82 in position thereon when the cam assumes the active position . alternatively , when the polarity of the electromagnet is reversed such that the pole 58 of the permanent magnet is attracted to the leg 41 and pole 56 is positioned adjacent the leg 40 , the follower end 82 is in engagement with the nominal region 66 such that the cam 52 now assumes the inactive position with tip end 84 no higher than the reference surface 32 ( right side of fig5 ). it should be noted that the length of the permanent magnet 54 is slightly greater than the distance between the legs 40 and 41 such that the magnet 54 can never become aligned with the bight 38 . thus the legs 40 and 41 serve as stops for the magnet 54 and thereby prevent it from becoming aligned with the unlike poles of the electromagnet 36 which might prevent the cam 52 from rotating in the desired direction . as seen especially clearly in fig2 and 4 , there are a total of six such tactile display devices with each comprising a cavity 28 and all of the components received therein provided with each tactile display unit 22 . the relative positioning of each of the cavities 28 is illustrated in fig4 to assure that the touch pins 80 are all properly aligned and the cavities are as large as possible to maximize the rise of the magnets . thus , it is noted that the electromagnets 36 of each of the devices are not parallel but are angularly disposed in order to achieve the desired alignment of the touch pins 80 . this also reduces magnetic interference from one cavity to its neighboring cavities . as seen in fig1 and 12 , each tactile display unit 22 has a total of twelve leads extending from opposite poles of each of the six electromagnets 36 therein . specifically , as previously explained , each electromagnet 36 has a positive lead and a negative lead , alternatively , 48 and 50 . each lead is suitably connected to an associated contact 92 ( fig2 and 3 ). also , as previously explained , with respect to fig1 a series of tactile display units 22 are provided on the console 20 for displaying a line of a computer output in braille characters . computers store information as a series of numbers which are represented as an 8 bit byte where each bit represents a digital switch that is either on ( high or &# 34 ; 1 &# 34 ;) or off ( low or &# 34 ; 0 &# 34 ;). these bits are numbered 0 - 7 and read from right to left where the rightmost bit is the least significant bit ( lsb ) and the leftmost is the most significant bit ( msb ). each bit is assigned a value which is 2 n where n = the bit position as follows : therefore , the byte ( 8 bits ) ` 01111010 ` is calculated by the computer ( from right to left ) as 2 + 8 + 16 + 32 + 64 which equals 122 . this is the ascii code for the letter &# 34 ; z &# 34 ;. using this system , the numbers 0 - 127 ( 0 through 2 7 - 1 ) represent a total of 128 valid ascii codes . table 1 is a representation of the braille character set . table 1__________________________________________________________________________ braille character set description__________________________________________________________________________1 o o 4 this is the basic brialle cell . the dots are referenced 1 - 62 o o 5 as indicated . 3 o o 6line 1 : o · o · o o o o o · o o o o o · · o · o · · o · · · · o · o o · o o o o o · o o · · · · · · · · · · · · · · · · · · · · a b c d e f g h i j1 2 3 4 5 6 7 8 9 0line 1 consists of the first 10 letters of the alphabet formed by theupperdots ( 1 , 2 , 4 , 5 ) of the braille cell . when preceded by the numericindicatorthese cells have the indicated numeric value . line 2 : o · o · o o o o o · o o o o o · · o · o · · o · · · · o · o o · o o o o o · o oo · o · o · o · o · o · o · o · o · o · k l m n o p q r s tline 2 adds dot 3 to each of the cells in line 1 . line 3 : o . o . o o o o o . o o o o o . . o . o . . o . . . . o . o o . o o o o o . o oo o o o o o o o o o o o o o o o o o o ou v x y z and for of the withline 3 adds dots 3 and 6 to each of the cells of the first line . line 4 : o . o . o o o o o . o o o o o . . o . o . . o . . . . o . o o . o o o o o . o o . o . o . o . o . o . o . o . o . o . och gh sh th wh ed er ou ow wline 4 adds dot 6 to each of the cells in the first line . also , theletter &# 34 ; w &# 34 ; was added here by braille to meet the needs of the english language . line 5 :. . . . . . . . . . . . . . . . . . . . o . o . o o o o o . o o o o o . . o . o . . o . . . . o . o o . o o o o o . o o , ; : . en ! ( ) &# 34 ;? in &# 34 ; line 5 represents the patterns of line 1 in the lower portion of thecell , using dots 2 , 3 , 5 , 6 . most of these characters have punctuation values . line 6 :. o . o . o . o . . . .. . . . . o . o . . . . o . o o o o o . o . o o / ing # ar &# 39 ; numberline 6 is formed with dots 3 , 4 , 5 , 6 . line 7 :. o . o . o . . . o . . . .. . . o . o . o . . . o . .. . . . . o . . . o . o . oused for two cell italic letter capitalcontractions sign ; sign sign decimal pointline 7 is formed of dots 4 , 5 , 6 . __________________________________________________________________________ treating braille dots 1 - 6 as a sequence of 6 bits with dot 1 being the least significant bit ( lsb , bit 0 ) and bit 6 as the most significant bit ( msb , bit 5 ) we can form a numeric representation for each braille character . since 2 of the bits are not used , ( 6 and 7 ) bit 6 , if set , will indicate a &# 34 ; capital letter &# 34 ;, bit 7 will indicate a &# 34 ; number &# 34 ;. this is required because braille uses the same codes for some characters . when printed , a &# 34 ; case &# 34 ; symbol ( letter , capitals , number ) will precede the character that is changing case . table 2 represents the ascii to braille conversion . table 2__________________________________________________________________________ascii td braille conversion ascii braille braille ascii braille braille decimal decimal binary decimal decimal binarycharacter value value value character value value value__________________________________________________________________________space 032 000 00000000 p 080 079 01001111 ! 033 022 00010110 q 081 095 01011111 &# 34 ; 034 052 00110100 r 082 087 01010111 # 035 074 00111100 s 083 078 01001110 $ 036 000 00000000 t 084 094 01011110 % 037 000 00000000 u 085 101 01100101 & amp ; 038 000 00000000 v 086 103 01100110 &# 39 ; 039 004 00000100 w 087 122 01111010 ( 040 054 00110110 x 088 109 01101101 ) 041 054 00110110 y 089 125 01111101 * 042 000 00000000 z 090 117 01110101 + 043 000 00000000 [ 091 000 00000000 , 044 002 00000010 092 000 00000000 045 036 00100100 ] 093 000 00000000 . 046 050 00110010 094 000 00000000 / 047 012 00001100 095 000 000000000 048 154 10011010 096 008 000010001 049 129 10000001 a 097 001 000000012 050 131 10000011 b 098 003 000000113 051 137 10001001 c 099 009 000010014 052 153 10011001 d 100 025 000110015 053 145 10010001 e 101 017 000100016 054 139 10001011 f 102 011 000010117 055 155 10011011 g 103 027 000110118 056 147 10010011 h 104 019 000100109 057 138 10001010 i 105 010 00001010 : 058 018 00010010 j 106 026 00011010 ; 059 006 00000110 k 107 005 00000101 & lt ; 060 000 00000000 l 108 007 00000111 = 061 000 00000000 m 109 013 00001101 & gt ; 062 000 00000000 n 110 029 00011101 ? 063 038 00100110 o 111 021 00010101 @ 064 000 00000000 p 112 015 00001111a 065 065 01000001 q 113 031 00011111b 066 067 01000011 r 114 023 00010111c 067 073 01001001 s 115 014 00001110d 068 089 01011001 t 116 030 00011110e 069 081 01010001 u 117 037 00100101f 070 075 01001011 v 118 039 00100111g 071 091 01011011 w 119 058 00111010h 072 083 01010011 x 120 045 00101101i 073 074 01001010 y 121 061 00111101j 074 090 01011010 z 122 053 00110101k 075 069 01000101 { 123 000 00000000l 076 071 01000111 | 124 000 00000000m 077 077 01001101 } 125 000 00000000n 078 093 01011101 126 000 00000000o 079 085 01010101 del 127 000 00000000__________________________________________________________________________ the ascii codes 0 through 31 represent handshake and control sequences that are non - printable and executed by the computer system . characters 32 through 127 are the printable character set . to convert ascii to braille , the code for an ascii letter must have a corresponding braille value . this is accomplished by creating a sequential list of elements within a computer program . this list of elements is known as an array . these array elements are sequentially numbered from 0 - 127 . therefore , if the ascii code for the letter &# 34 ; z &# 34 ; is 122 , the program will read array element 122 and extract the number 65 which is the braille equivalent . as indicated in table 1 , special braille characters exist that change the case of the letters that follow . when designing a braille character display , firmware would have to be developed that recognizes the case of the character and , if there is a case change , the braille control code would be inserted into the character string that changes the case . the translated character string would then be passed along a six bit data bus for display on the braille unit . driver circuitry would be developed that would correlate a logic 1 ( high ) to a positive voltage that would raise a desired pin and a logic 0 ( low ) as a negative voltage that would lower a desired pin . while a preferred embodiment of the invention has been disclosed in detail , it should be understood by those skilled in the art that various modifications may be made to the illustrated embodiment without departing from the scope as described in the specification and defined in the appended claims .