in the following m - sequence generators are described as an example of a pn sequence generator , but other types of pn sequence generators might be just as applicable . fig1 shows a schematic block diagram of a prior art generator . this figure has already been explained above . fig2 shows four clock controlled pn sequence generators / generation means ( 201 ) generating an output pn sequence according to the invention . preferably , the sequence generation means ( 201 ) are m - sequence generators . the clocking of each generator ( 201 ) is controlled by a sequence c k = c k 0 , c k 1 , c k 2 , . . . , of symbols each representing the value 0 or 1 , i . e . c k t ε { 0 , 1 } where t denotes the time instants 0 , 1 , 2 , . . . and k denotes the index of the generators ( 201 ), i . e . 1 , 2 , 3 , and 4 in this example . the sequence c k t is denoted clock signal which consists of clock values forming the sequence . if the k &# 39 ; th m - sequence generator ( 201 ) steps once every time instant , the generator ( 201 ) will produce the simple sequence x k = x k 0 , x k 1 , x k 2 , x k 3 , . . . . if the stepping is controlled by the values of the symbols of c k , the following output sequence z k = z k 0 , z k 1 , z k 2 , z k 3 , . . . , will be produced : z k t = x k σ ( k , t ) t = 0 , 1 , 2 , 3 , . . . , and the sum σ goes from i = 0 to i = t − 1 and k = 1 , 2 , 3 , 4 . in other words , the next symbol z k j is equal to either the next symbol x k m ( if c k t = 1 ) or the next symbol again x k m + 1 ( if c k t = 2 ). as an example , the sequence z k 0 = x k 0 , z k 1 = x k 2 , z k 2 = x k 4 , z k 3 = x k 5 will be output if c k 0 = 1 or 2 ( does not matter ), c k 1 = 2 , c k 2 = 2 , c k 3 = 1 . the four output sequences z 1 , z 2 , z 3 , z 4 are combined by function generation means ( 203 ) which applies a given function f to the sequences z 1 , z 2 , z 3 , z 4 in order to obtain one single output sequence out = out 0 , out 1 , out 2 , out 3 , . . . . hereby , one single pn sequence is obtained and used as output sequence arising from a combination of the four single pn sequences , thereby enhancing the unpredictability even further . alternatively , other kinds of functions may be applied instead of the above one , e . g . a simple way of selecting one of the single pn sequences . the clocking signals c 1 t , c 2 t , c 3 t , c 4 t , responsible for controlling the generators ( 201 ), form the step pattern ( c 1 t , c 2 t , c 3 t , c 4 t ) for each time instant . the clocking signals are derived by a step pattern subsystem ( 202 ) which receives a step control signal ( u k t ) from each generator ( 201 ). the step control signal ( u k t ) preferably depends on the clocking signal ( c k t ). the step pattern subsystem / step pattern generation means ( 202 ) will be described in detail in connection with fig3 . the number of generators that may be used in connection with the present invention may be any number , and four just serves as an example . fig3 shows a step pattern subsystem ( 202 ) according to one embodiment of the invention . the implementation shown in fig3 is only one possible implementation of the step pattern subsystem ( 202 ). the subsystem ( 202 ), also denoted step pattern generation means , receives four step control values u 1 t , u 2 t , u 3 t , u 4 t at each time instant . the step control values together with the clocking signals c 1 t , c 2 t , c 3 t , c 4 t are used to obtain a single combined value u t by the combination means ( 302 ). the combined value ( u t ) denotes a value in the range 0 , 1 , 2 , 3 . preferably , the following 6 possible stepping patterns are chosen : ( 0 , 0 , 1 , 1 ), ( 0 , 1 , 0 , 1 ), ( 1 , 0 , 0 , 1 ), ( 0 , 1 , 1 , 0 ), ( 1 , 0 , 1 , 0 ), ( 1 , 1 , 0 , 0 ). these 6 stepping patterns have the advantages of stepping the four connected generators ( 201 ) uniformly , thereby enhancing the unpredictability , since no single generator ( 201 ) is stepped more often than others on average . another advantage is that only two generators ( 201 ) are stepped at the same time , thereby reducing the power consumption in the electrical device , which is an advantage especially in portable devices like mobile telephones which have a limited power source . these 6 possible stepping patterns are just an example and any number or combination is applicable . preferably , u t is derived in the following way dependent on the value of the previous c t : any kind of other relationships may be used to derive the combined value ( u t ). a step pattern select signal ( w t ), responsible for selecting the step pattern being forwarded to the generators ( 201 ) in pattern select means ( 301 ), is derived based on the combined value ( u t ) and a previous generated step pattern select signal ( w t − 1 ). the previous generated step pattern select signal ( w t − 1 ) is held in a delay element ( 304 ). the derivation of the step pattern select signal ( w t ) is done in the add / mod means ( 303 ), receiving the combined value ( u t ) and a previous generated step pattern select signal ( w t − 1 ), in the following way : w t − 1 = u t + w t − 1 mod 6 . the step pattern select signal ( w t ) takes a value in the range 0 , 1 , 2 , 3 , 4 , 5 . in an alternative embodiment , the step pattern select signal ( w t ) is derived on the basis of the combined value ( u t ) and a plurality of previously generated step pattern select signal w t − 1 , w t − 2 , w t − 3 , . . . , giving even better properties with respect to unpredictability . for example , the step pattern select signal ( w t ) may be derived as : u t + a 1 w t − 1 + a 2 w t − 2 + a 3 w t − 3 mod 6 , where a 1 , a 2 , and a 3 are pre - selected constants suitable for a given application . in cases where the number of selectable patterns is not a prime number , the computation of the step pattern select signal ( w t ) may advantageously be implemented using a chinese remaindering technique . for the example of 6 possible stepping patterns , the step pattern select signal ( w t ) can be derived by simultaneously computing : w 1 t = u t + w 1 t − 1 mod 2 , t = 0 , 1 , 2 , . . . w 2 t = u t + w 2 t − 1 mod 3 , t = 0 , 1 , 2 , . . . where w 2 t − 1 = w t − 1 mod 2 and w 1 t − 1 = w t − 1 mod 3 , by using 6 prime number factors ( 6 = 2 × 3 ). fig4 shows a generalized embodiment of clock controlled pn sequence generators . shown is a plurality of n pn - sequence generators ( 201 ) and a step pattern subsystem ( 402 ), which may in functionality correspond to the step pattern system ( 202 ) shown in fig2 but adapted to obtain n step control signal ( u t 1 . . . u t n ) from the n pn - sequence generators ( 201 ). the step pattern subsystem ( 402 ) provides the n pn - sequence generators ( 201 ) with n clocking signals ( c t 1 . . . c t n ) responsible for clocking / controlling the pn - sequence generators ( 201 ) by applying a functionality e . g . similar to the one explained in connection with fig3 . the generalized step pattern subsystem ( 402 ) will be described in connection with fig5 . also shown is function generation means ( 403 ) which applies a given function f to the sequences z 1 , z 2 , . . . z n in order to obtain one single output sequence out = out 0 , out 1 , out 2 , out 3 , . . . , e . g . as described in connection with fig2 . fig5 shows a generalized embodiment of the step pattern subsystem . shown is a step pattern subsystem corresponding to the system ( 402 ) in fig4 which selects one step pattern comprising n clocking signals c t among a plurality of possible step patterns . the step pattern subsystem receives n step control values u 1 t , u 2 t , . . . , u n t at each time instant from n pn - sequence generators ( 401 ), where u i t is 0 or 1 in the simplest case for i = 1 . . . n . the step control values are used together with a previous step pattern / clocking signals c 1 t , c 2 t , . . . , c n t from pattern select means ( 501 ) by combination means ( 502 ) in order to obtain a single combined value u t . a step pattern select signal ( w t ), responsible for selecting the step pattern being forwarded to the generators ( 401 ) by the pattern select means ( 501 ), is derived based on the combined value ( u t ) and a previous generated step pattern select signal ( w t − 1 ). the previous generated step pattern select signal ( w t − 1 ) is held in a delay element ( 304 ). the derivation of the step pattern select signal ( w t ) is done in the combine input means ( 503 ), receiving the combined value ( u t ) and a previous generated step pattern select signal ( w t − 1 ). the derivation of the step pattern select signal ( w t ) may be realized in many ways depending of a particular implementation of the invention and may e . g . be derived as an addition mod m , where m is the number of possible step patterns , as described in connection with fig3 ( where m = 6 ). the m step patterns may be chosen as suitable clock patterns of all the possible combinations of subsets containing k elements from a set of n elements . a subset refers to the k pn - sequences generators to be clocked . in general , for a given k all the values between k min and k max , with n ≧ kmax ≧ kmin ≧ 1 , may be chosen , giving m = ∑ k = k min k = k max   n ! k !  ( n - k ) ! for the embodiments in fig2 and 3 the values was : n = 4 , k = 2 , kmax = kmin = 2 . as mentioned , the embodiments shown in fig2 and 3 is a specialized case of the embodiments shown in fig4 and 5 and many other embodiments may just be as applicable depending on a specific implementation and should not limit the scope of the invention as sought out in the appended claims . fig6 shows a flow chart of the method according to the invention . the method generates a plurality of pn sequence values / symbols and selects one of these as output . as an example , a method using four generators will be described . at step ( 602 ) one step pattern is selected on the basis of a step pattern select signal ( w t ) from a plurality of possible step patterns . the generation of the step pattern select signal ( w t ) will be described later in connection with step ( 606 ). the step pattern chosen is responsible for controlling the mode according to which the pn sequence generators will generate a output sequence value ( z t ), as will be described later . preferably , the following 6 possible stepping patterns are chosen : ( 0 , 0 , 1 , 1 ), ( 0 , 1 , 0 , 1 ), ( 1 , 0 , 0 , 1 ), ( 0 , 1 , 1 , 0 ), ( 1 , 0 , 1 , 0 ), ( 1 , 1 , 0 , 0 ). these 6 possible stepping patterns have the advantage that only two generators is clocked at a time , thereby reducing the computational complexity of the method at a given time instance . another advantage is that the 6 possible stepping patterns clock the generators uniformly , thereby enhancing the unpredictability , since no generator is used to output a sequence value more often than the others . at step ( 603 ) a plurality of clock values ( c t ) is provided to the generators on the basis of the selected step pattern . the step pattern comprises the individual clock values for each generator , e . g . the step pattern ( 0 , 0 , 1 , 1 ) will control the two first generators to step once ( generate the next symbol ) and control the two last generators to step twice ( generate the second next symbol ). after receiving the clock values ( c t ), the generators each generate a pn sequence value according to the received clock value c t at step ( 604 ). at step ( 605 ) a function f is applied to combine the four output sequences z 1 , z 2 , z 3 , z 4 in order to obtain one single output sequence out = out 0 , out 1 , out 2 , out 3 , . . . . where z k t denotes a sequence value ( z t ) generated by the k &# 39 ; th generator . in this way , a single sequence value ( out t ) is obtained which relates to all the generated sequence values ( z t ), thereby enhancing the unpredictability of the output sequence ( out t ) even further . other functions than the one described above may be applied just as well . at step ( 606 ) a plurality of step control values ( u t ) is provided from the plurality of generators . these step control values ( u t ) together with the clock values ( c t ) are used to derive a combined value ( u t ) which is used to calculate the step pattern select signal ( w t ) as described in connection with the device according to the invention . preferably , the generators are standard m - sequence generators , e . g . implemented in software , but other types of pn sequence generators may be used instead . alternatively , some of the steps may be executed simultaneously , e . g . the steps ( 603 ) and ( 606 ). fig7 shows a preferred embodiment of the invention , which may contain the electrical device and / or use the method according to the present invention . shown is a mobile telephone ( 701 ) having display means ( 704 ), a keypad ( 705 ), an antenna ( 702 ), a microphone ( 706 ), and a speaker ( 703 ). by including the electrical device and / or the method according to the present invention a safer encryption of speech signal is provided , just requiring very little additional hardware and / or additional computational effort . fig8 a shows a communications system ( 801 ) comprising a first transmitting / receiving station ( 803 ) and a second transmitting / receiving station ( 804 ) where information ( 805 ) may be transmitted . the pn sequences generated by the device or method according to embodiments of the present invention may be used as a subcomponent to encrypt information ( 805 ) to be transmitted between the first transmitting / receiving station ( 803 ) and the second transmitting / receiving station ( 804 ). in this way , a safer transmission of information ( 805 ), like data , digitized speech signals , etc ., may be achieved with reduced power consumption and / or reduced computational complexity . fig7 b shows a transmitting / receiving station ( 803 ) and a mobile terminal ( 701 ) which form a cellular communications system ( 802 ). the information ( 805 ) to be transmitted / received between the mobile terminal ( 701 ) and a network infrastructure ( not shown ) via the transmitting / receiving station ( 803 ) may be encrypted through the use of a ciphering system that uses pn sequences generated by clock controlled m - sequence generators . in this way , safe transmission of information ( 705 ), like data , digitized speech signals , etc ., may be achieved by using less hardware , thereby reducing the costs and power consumption . although various embodiments of the invention are described herein , it should be recognized that the invention maybe varied in numerous ways . accordingly , it should be understood that the invention should be limited only insofar as is required by the scope of the following claims .