Single button contrast control

A single button contrast control which can bi-directionally adjust a contrast function in one of two directions so as to increase or decrease the contrast of a display. An interrupt generator generates an interrupt for each user activation of a single button control key. A control circuit incrementally adjusts the contrast function in accordance with the interrupts generated. If no interrupts are generated within a predetermined period of time following a previous interrupt, the control circuit changes the direction in which the contrast is incrementally adjusted so that the next time a user activates the single button control key the control will be adjusted in the other direction.

TECHNICAL FIELD 
The present invention relates generally to switching devices, and in 
particular to a single button switch for use in bi-directionally 
controlling a function of a computing device. 
BACKGROUND OF THE INVENTION 
In recent years, the use of wireless communication systems having mobile 
transceivers which communicate with a hardwired network, such as a local 
area network (LAN) or a wide area network (WAN), has become widespread. 
The mobile transceivers, commonly referred to as mobile terminals, may 
take one of several different forms. For instance, in retail stores 
hand-held scanning units may be used to allow for scanning inventory bar 
codes. In a warehouse, portable units mounted to a vehicle may be used to 
gather information from the warehouse floor. In a medical environment, the 
mobile terminal may take the form of a pen based workslate which allows 
medical personnel to work with full page screens. 
In a typical wireless communication system, each mobile terminal 
communicates with a networked system via a radio or optical link in order 
to allow for a real time exchange of information. The mobile terminals 
communicate through one of several base stations interconnected to the 
network. The base stations allow for a wireless data communication path to 
be formed. Consequently, such mobile terminals significantly facilitate 
worker efficiency since data can be gathered, transmitted and even 
processed at a remote site in real time. 
However, despite the aforementioned advantages associated with mobile 
terminals, there is a strong need for a more ergonomic mobile terminal. 
For example, with the widespread use of computers, portable digital 
assistants, and the like there is an ongoing struggle to enhance display 
systems to allow for user friendly viewing of information on the screen. 
One standard feature available on many electronic devices to accommodate 
user friendly viewing is a contrast control. The contrast control allows a 
viewer to lighten or darken the display screen to adjust for current 
ambient lighting conditions. For instance, on particularly sunny days a 
viewer of a display screen may choose to darken the screen to allow for 
easier readability. Alternatively, as the day gets darker the viewer may 
choose to lighten the screen. 
Furthermore, many such mobile terminals have liquid crystal displays (LCDs) 
and as they are moved from one point to another the LCD may be exposed to 
temperature variances which affect the LCD contrast. For example, extreme 
cold renders the liquid crystal material opaque and extreme heat renders 
the material transparent. Consequently, some form of contrast control is 
required to compensate for the effects of temperature variances on the 
liquid crystal display. 
To adjust the contrast control, manufacturers of electronic devices 
(including mobile terminals) typically include two easily accessible 
contrast control buttons. One of the contrast control buttons would be 
used for darkening the screen and another of the contrast control buttons 
would be used to lighten the screen. As opposed to using buttons, there 
have also been electronic devices made with rotatable knobs and sliding 
controls which provide for similar functionality. For instance, by either 
turning or sliding such a control, the contrast on the screen would adjust 
appropriately. 
One area of growing popularity in the computer industry is the use of 
wireless pen based computer systems. Such computers are used by workers in 
warehouses and on manufacturing floors as well as outdoors by postal 
workers, utility servicemen, etc. Given the environment in which such 
mobile terminals are often utilized, it is not beneficial to provide a 
contrast control feature which uses rotatable or sliding controls since 
such controls are prone to breaking and often provide an inlet where rain 
or other moisture is able to seep into the computer and damage internal 
wiring. Buttons are more durable and easier to secure from moisture, 
however, since two buttons are needed this often takes up a significant 
portion of valuable space on the mobile terminals control panel. This is 
especially true of mobile terminals built for ruggidized outdoor activity 
since each button on the portable computer is oversized and spaced apart 
to allow for easy management by individuals who may be wearing gloves or 
the like. 
The portability of these computing devices places demands on reduction of 
size. In order to meet this demand, it is desired to optimize the key 
board arrangement of such devices so as to optimize space. A single button 
switch is known in the art for bi-directionally controlling volume. 
However, there are deficiencies associated with this conventional switch. 
In particular, the switch must be continuously depressed in order to 
increase or decrease the volume. Once the button is released, the volume 
direction is changed so that the next time the button is pushed the volume 
moves in the opposite direction. A problem with such a design is overshoot 
and undershoot of a desired function level. For example, if a user desires 
to increase the volume he/she must keep the button depressed. If the 
button is pressed too long, the volume is set to be excessively louder 
than desired. If the button is not pressed down long enough the volume is 
too low. In the case where the button is not pressed down long enough, the 
next time the user pushes down the button the volume is further reduced. 
Consequently, fine tuning of the volume is not achieved as easily as if 
two buttons were available (one for each direction of change in volume). 
Thus, in light of the above, there is a strong need for a single button 
switch which can accomplish substantially the same amount of functions 
that can be accomplished conventionally with two switches and avoid the 
problems associated with conventional single button switches. In 
particular, there is a need in the art for a contrast control feature 
which does not have the limitations described above. More specifically, 
there is a need for a single button contrast control feature which is 
durable, easy to seal, requires a minimum amount of space, and affords for 
fine tuning a function easily. 
SUMMARY OF THE INVENTION 
The present invention describes a single button control system which 
overcomes the shortfalls described above with known function control 
techniques. In particular, the present invention is directed to a single 
button contrast control which can bi-directionally adjust a contrast 
function in one of two directions so as to increase or decrease the 
contrast of a display. An interrupt generator generates an interrupt for 
each user activation of a single button control key. A control circuit 
incrementally adjusts the contrast function in accordance with the 
interrupts generated. If no interrupts are generated within a 
predetermined period of time, the control circuit changes the direction in 
which the contrast is incrementally adjusted so that the next time a user 
activates the single button control key the control will be adjusted in 
the other direction. 
In accordance with one particular aspect of the present invention, a 
switching system is provided, including: a user activated switch for 
shifting among a plurality of levels, the shifting occurring in accordance 
with one of a first state and a second state, and the switch operable to 
switch between the first state and the second state; a control circuit 
operative to receive a signal from the switch; wherein the signal from the 
switch generates an interrupt in the control circuit so as to trigger the 
control circuit to effect shifting among the plurality of levels. 
According to another aspect of the present invention, an electronic device 
is provided, including: a user activated switch for selectively 
controlling at least one function of the electronic device, the function 
having a plurality of function levels, the at least one function having a 
first direction state and a second direction state; and a control circuit 
operative to receive a signal from the switch, the control circuit 
controlling the plurality of function levels in accordance with the signal 
from the switch, and wherein the control circuit shifts from the first 
direction state to the second direction state following inactivity of the 
switch for a predetermined period of time. 
In accordance with another aspect of the present invention, a portable 
computing device having a single button function control, comprising: a 
portable housing; a control circuit within the housing, the control 
circuit including a user programmable processor; a display visible through 
an opening in said housing; at least one single button control key coupled 
to the control circuit for selectively controlling at least one function 
of the portable computing device, the at least one function having a first 
direction state, a second direction state, and a plurality of function 
levels, the control circuit operative to receive a signal from the at 
least one single button control key, the control circuit controlling a 
plurality of function levels in accordance with the signal from the at 
least one single button control key, and wherein the control circuit 
shifts from the first direction state to the second direction state 
following inactivity of the switch for a predetermined period of time. 
To the accomplishment of the foregoing and related ends, the invention, 
then, comprises the features hereinafter fully described and particularly 
pointed out in the claims. The following description and the annexed 
drawings set forth in detail certain illustrative embodiments of the 
invention. These embodiments are indicative, however, of but a few of the 
various ways in which the principles of the invention may be employed. 
Other objects, advantages and novel features of the invention will become 
apparent from the following detailed description of the invention when 
considered in conjunction with the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will now be described with reference to the drawings, 
wherein like reference numerals are used to refer to like elements 
throughout. 
As is mentioned above, the present invention relates to a single button 
control system which overcomes the shortfalls described above with known 
function control techniques. In particular, the present invention is 
directed to a single button contrast control which can bi-directionally 
adjust a contrast function in one of two directions so as to increase or 
decrease the contrast of a display. An interrupt generator generates an 
interrupt for each user activation of a single button control key. A 
control circuit incrementally adjusts the contrast function in accordance 
with the interrupts generated. If no interrupts are generated within a 
predetermined period of time, the control circuit changes the direction in 
which the contrast is incrementally adjusted so that the next time a user 
activates the single button control key the control will be adjusted in 
the other direction. The use of interrupts to handle a single button 
control feature has advantages over non-interrupt driven systems given the 
reduced need for digital logic circuitry and since they are easily 
configurable with existing interrupt driven functionalities of a device. 
The present invention will now be described with reference to the drawings 
wherein like reference numerals are used to refer to like elements 
throughout. 
As is mentioned above, the present invention relates to a programmable 
mobile terminal (e.g., a portable teletransaction computing device (PTC)) 
in which a single button switch is used to bi-directionally control a 
function (e.g., the contrast of a display) of the PTC. In the exemplary 
embodiments described hereinafter, each PTC is a hand held inventory 
control device used to communicate data such as inventory or the like 
within a cellular, narrow band or other radio communication system 
including multiple mobile terminals and base stations. However, it is 
recognized that the present invention contemplates other types of 
programmable mobile terminals or devices and portable computers and is not 
intended to be limited necessarily to hand held inventory control devices 
or devices which must wirelessly communicate information. 
Referring initially to FIG. 1, a mobile terminal 10 is shown in accordance 
with the present invention. The terms "mobile terminal", "PTC" and 
"portable computer" are used interchangeably throughout the specification. 
The mobile terminal 10 includes a portable housing 12 which is preferably 
made of metal, high strength plastic, or the like. The mobile terminal 10 
includes a display 14 such as a liquid crystal display (LCD) or the like. 
In the preferred embodiment, the display 14 is a fine pitch liquid crystal 
display operated as a standard CGA display with a resolution of 
640.times.200 pixels. As is conventional, the display 14 functions to 
display data or other information relating to ordinary operation of the 
mobile terminal 10 in a cellular communication system. For example, the 
display 14 may display inventory information, pricing detail, etc. which 
is to be transmitted to or is received from a system backbone. 
Additionally, the display 14 may display a variety of functions that are 
executable by the mobile terminal 10. The display 14 is capable of 
displaying both alphanumeric and graphical characters. 
The mobile terminal 10 further includes an operator input device 18 in the 
form of a key pad which enables a user to enter data, information, 
function commands, etc. as is conventional. For example, the user may 
input information relating to inventory via the keypad 18 for subsequent 
transmission to a base station (not shown). In addition, the keypad 18 
includes up and down cursor keys 20a and 20b, respectively, for 
controlling a cursor which may be shown on the display 14. By selectively 
pressing the up and down cursor keys 20a and 20b, the user is able to move 
the cursor about the display 14. Furthermore, the key pad 18 includes a 
select key 20c for selecting an item or function designated by the cursor. 
The mobile terminal 10 also includes a bar code reader 22 in the form of a 
wand or the like which allows information to be input to the mobile 
terminal 10 via bar code symbols. The bar code reader 22 is coupled to the 
housing 12 by a cable 24 which provides the appropriate electrical 
connections between the bar code reader 22 and the circuitry contained in 
the housing 12. 
Extending from the housing 12 is an antenna 28 for transmitting and 
receiving radio signals within a cellular communication system. In the 
exemplary embodiment, the antenna 28 is an omnidirectional antenna but 
other types of antennas may equally be used. A speaker 29 is integral to 
the housing 12 and provides an audial output for the user. Additionally, 
the mobile terminal 10 includes a PCMCIA card slot 30 for receiving a 
PCMCIA card. As mentioned above, the mobile terminal 10 is user 
programmable and thus a user can input commercial or user created software 
to tailor the mobile terminal 10 to execute desired functions. However, it 
is understood that this invention is not limited to inputting functions, 
instructions or data via a PCMCIA card, and that any suitable means for a 
user to input functions, instructions or data to the mobile terminal 10 
falls within the scope of the this invention. 
Information may be entered into the mobile terminal 10 in a number of 
different manners. For instance, information may be entered through the 
bar code reader 22, the keypad 18, or even through the display screen 14. 
Further, a series of push button input keys 40a-d are also available to 
perform certain specified operations. For instance, in the present 
embodiment, input key 40a is for contrast control, input key 40b is to 
place the mobile terminal 10 into a power savings suspend mode, input key 
40c is used to toggle a back light to the display screen 14, and input key 
40d serves as a right mouse button to provide for extra functionalities 
when working in a Windows (TM) environment on the mobile terminal 10. It 
will be appreciated that a thumb wheel (not shown) could be employed in 
lieu of the mouse to provide for extra functionalities. The push button 
keys 40a-d in the preferred embodiment are spring loaded, however, any 
suitable type of mechanical and/or electrical key may be employed to carry 
out the present invention. 
Referring now to FIG. 2, a block diagram of the electronic circuitry within 
the mobile terminal 10 is shown. As noted above, the mobile terminal 10 
includes an antenna 28 for receiving and transmitting signals via a 
transceiver 40 to which it is connected. The transceiver 40 is coupled via 
a control/data bus 42 to a processor 44 included in the mobile terminal 
10. The processor 44 is responsible for controlling the general operation 
of the mobile terminal 10 with respect to processing and storing 
information received and transmitted by the transceiver 40. The processor 
44 is programmed to control and to operate the various components within 
the mobile terminal 10 in order to carry out various functions described 
herein. The operator input device 18 is coupled to the processor 44 which 
allows an operator to input data to be communicated to a system backbone 
(not shown) or local computer (not shown) such as inventory data, ordering 
information, and the like. The input device 18 can include such items as 
the aforementioned keypad, touch sensitive display, etc. The mobile 
terminal 10 also includes the bar code reader 22 coupled to the processor 
44 for providing another form of data input. 
The display 14 is connected to and controlled by the processor 44 via a 
display driver circuit 46. A memory 50 is included in the mobile terminal 
10 for storing program code executed by the processor 44 for carrying out 
operating functions of the mobile terminal 10 as described herein. The 
memory 50 may also serve as a storage medium for temporarily storing 
information received from or intended to be transmitted to a base station 
(not shown) or a local computer (not shown). The memory 50 includes 
various memory areas and system resources. These various memory areas 
include a main memory, a nonvolatile memory or Boot ROM, an extended 
memory, an expanded memory, and battery backed random access memory 
(typically implemented as a complementary metal oxide semiconductor device 
or CMOS device). 
Main memory is the normal random access memory which is used by both 
applications and systems software of the mobile terminal 10. Main memory 
includes a system management area comprising a segment of isolated random 
access memory. The system management area may only be accessed while the 
processor 44 is in a system management interrupt state. As will be 
discussed in greater detail below, the system management interrupt state 
is entered upon the occurrence of a system management interrupt. The 
remaining portions of main memory are freely accessible (i.e., 
non-isolated) by any interrupt or noninterrupt processing logic. 
A power supply 52 is also included in the mobile terminal 10 for providing 
power to the various components of the mobile terminal 10 as is 
conventional. The power supply 52 may be in the form of a battery and/or 
connectable to an external power source such as a wall outlet. 
With the exception of the antenna 28, the components making up the mobile 
terminal 10 are preferably housed in a palm-sized housing 12 represented 
in phantom. This makes the mobile terminal 10 highly portable and easy to 
carry from one cell to another within a cellular system. 
Also coupled to the processor 44 through a push button interface 60 are the 
input keys 40a-40d. The push button interface 60 serves as a debouncer for 
the input keys 40a-40d and provides the processor 44 with an address 
signal along line 64 which the processor 44 monitors so as to determine 
when and which of the input keys 40a-40d has been pressed. Also coupled to 
the processor 44 via an interrupt handler 66 is a push button interrupt 
generator 68. 
The push button interrupt generator 68 generates an interrupt signal to the 
processor 44 each time an input key 40a-40d is pressed so that the 
processor 44 knows when to check the address on line 64. Until a push 
button interrupt is sent to the processor 44, the processor 44 does not 
investigate the status of the input keys 40a-40d via line 64 and thus any 
inputs through these keys would be ignored without the push button 
interrupt generator 68. The signal on line 64 will vary in accordance with 
the particular input key 40a-40d pressed. In the preferred embodiment, the 
processor 44 discriminates between which input key 40a-40d by the voltage 
level of the signal on line 64. However, any suitable means for allowing 
the processor 44 to determine which key is being pressed may be used to 
carry out the present invention. 
Independent of the push button interrupt generator 68, but also coupled to 
the processor 44, is a periodic system management interrupt (SMI) 
generator 80. The purpose of the SMI generator 80 is to effect continuous, 
systematic interrupts to the processor 44 for the purpose of maintaining a 
direction change counter (DCC) 90 discussed below. System management 
interrupts differ from most other types of interrupts in that they are 
completely independent of the application program running on the mobile 
terminal 10. Thus, even if new software is loaded to the mobile terminal 
10 or if the mobile terminal 10 is configured with a new operating system, 
the SMI generator 80 will independently continue to assert its system 
management interrupts to the processor 44. Accordingly, system management 
routines may be prompted for execution at a programmable rate with minimal 
system overhead. In the preferred embodiment, the SMI generator 80 is set 
to trigger an interrupt every 1/8th of a second. However, it will be 
appreciated that any suitable frequency of interrupt generations may be 
employed to carry out the present invention, and fall within the scope of 
the present invention as recited in the claims. 
The memory 50 which is coupled to the processor 44 includes memory 
locations for both a direction flag 100 and the direction change counter 
90. As will be discussed below in conjunction with FIG. 3, the direction 
change counter 90 is loaded with its full value each time the contrast 
input key 40a is pressed (see step 210). The direction change counter 90 
sets a time limit that a user pressing the contrast input key 40amay 
pause. If the user pauses between pressing the contrast input key 40a for 
more then the time limit afforded (as governed by the combination of the 
direction change counter 90 and the periodic SMI generator 80), the 
direction flag 100 will toggle the direction the contrast is adjusted. In 
other words, if the contrast key 40a is not pressed within the time limit 
(e.g., 1 second), the direction flag 100 will switch the direction the 
contrast is being adjusted. For example, if a user is incrementally 
increasing (e.g., brightening) contrast by repeatedly pressing the 
contrast button 40a, and then does not press the contrast button for the 
time limit (e.g., 1 second), the direction flag 100 will toggle and switch 
the direction of the contrast function. Thus, when the user presses the 
contrast key 40a again, the contrast will decrease (e.g., darken) as the 
contrast key 40a is pressed. If the user thereafter pauses again for a 
period of time exceeding the limit, the direction flag 100 will toggle 
again to switch the direction so that contrast is increased as key 40a is 
pressed. This process is repeated continuously after the mobile terminal 
10 has been activated and the contrast key 40a has been pressed at least 
once. 
In particular, a typical value for the direction change counter 90 may be 
seven or eight, thereby giving the user adjusting the contrast a one 
second total allowable pause time before the direction flag 100 is toggled 
assuming the periodic SMI generator 80 generates an interrupt every 1/8th 
of a second. As an example, a user desiring to adjust the contrast of the 
display 14 would begin by pressing and depressing the contrast input key 
40a. If the person wished to continue adjusting the contrast in the same 
direction, he/she would have to again press the contrast input key 40a in 
less then the one second time interval preset. Adjustment in the same 
direction would continue to occur as long as the contrast input key 40a 
was pressed and depressed in less then the one second time. If, however, 
the person paused for over one second before again pressing the contrast 
input key 40a, the direction flag 100 will have toggled thereby resulting 
in the contrast adjusting in the opposite direction. From this point on 
the contrast will continue adjusting in this new direction until a pause 
of over one second is sensed between pressings of the contrast input key 
40a. 
Finally, the display 20 is shown coupled to the processor 44 through a 
display driver 46. The display driver 46 includes a digital to analog 
(D/A) converter (not shown). The contrast of the display 14 is governed by 
the value of a four bit binary value input to the display driver 46 via 
line 110. A representative analog value is output from the display driver 
46 to the display 20 via line 116 which controls the contrast level of the 
display 14. The method in which the contrast of the display 14 is adjusted 
is well known in the art and follows conventional techniques. 
FIG. 3, is an overall block diagram of the operations of the mobile 
terminal 10 with respect to adjusting the contrast level of the display 14 
in accordance with the present invention. Beginning in step 300, the 
processor 44 starts power-on and general initializations as part of the 
overall initializations of the mobile terminal 10. Such initializations 
are conventionally known and are not further discussed for sake of 
brevity. In step 310, the interrupt generator 68 passively monitors the 
mobile terminal 10 for any pressing of the contrast key 40a. It will be 
appreciated that the interrupt generator 68 monitors for the pressing of 
other keys such as 40b-40d. If the contrast key 40a has not been pressed, 
the processor 44 returns to step 310. If the interrupt generator 68 
determines that the contrast key 40a has been pressed, it sends in 
interrupt to the processor 44 in step 320. Upon sensing that the contrast 
input key 40a is pressed, the processor 44 proceeds to step 330 where it 
reloads the direction change counter 90 in memory 50 with a preset value. 
In the preferred embodiment, the preset value is eight, thereby providing 
that any pause for more than one second will result in the direction flag 
100 being toggled. As was mentioned above, the periodic SMI generator 80 
will generate a system management interrupt every 1/8th of a second. Since 
each SMI interrupt decrements the DCC 90 by one, the DCC will reach 0 
after 1 second passing where the contrast key 40a is not activated. It is 
noted that upon start up, the direction flag is preloaded with a default 
"increase" value while the direction change counter is set to zero at 
start up. 
Following step 330, the processor 44 advances to step 340 where it 
determines which direction the direction flag 100 is currently set. If the 
direction flag 100 is set to increase, the processor 44 goes to step 350 
where the contrast of the display 14 is adjusted one increment to increase 
if possible. In some cases it may not be possible to increase the contrast 
of display 14 since a maximum contrast value may already have been 
reached. Alternatively, if it is determined in step 340 that the direction 
flag 100 is not set to "increase", then the direction flag 100 must be set 
to "decrease" and the processor 44 moves instead to step 360. In step 360 
the processor 44 decreases the contrast on the display screen 14 by one 
increment if possible. Finally, after either step 350 or step 360 is 
completed, the process is returned to step 310. 
FIG. 4 shows the operations which govern the direction of the direction 
flag 100. In step 400, the processor 44 determines if an SMI interrupt is 
generated by the periodic SMI generator 80. As discussed above, the period 
SMI generator 80 in the preferred embodiment is set to trigger eight times 
every second. If an SMI interrupt is detected by the processor 44, the 
processor 44 proceeds to step 410 where the processor determines if the 
direction change counter (DCC) 90 equals zero. If in step 410 the DCC 90 
equals zero then that indicates that there has been no activity with 
respect to the contrast input key 40a being pressed recently, and thus the 
processor 44 moves to step 450 and ends the routine. Note that if the 
contrast input key 40a had been pressed recently, then the DCC 90 would 
have been loaded with the value eight in step 330 (FIG. 3), as discussed 
above. If, in step 410 the DCC 90 is not zero, then the processor 44 in 
step 420 decrements the DCC 90 by one and continues to step 430. In step 
430, the processor 44 again checks if the DCC equals zero. If it does not, 
the processor 44 simply ends this routine by proceeding to step 450. If 
the DCC 90 does equal zero then the processor 44 continues to step 440 
where the direction flag 100 is toggled. After step 440, the processor 44 
ends the routine in step 450. 
The present invention via the system interrupts affords for incrementally 
moving along a direction of a particular function (e.g., contrast 
control). As a result, a user is able to fine tune a particular function 
with ease. For example, by way of the present invention, a user could push 
the contrast control key 40a until a desired level of contrast is reached. 
By allowing a user to incrementally move along a direction of a function 
with each push of the key 40a, the present invention makes fine tuning of 
the function much easier as compared to conventional devices. In other 
words, since a user is not required to keep the key 40a continuously 
pressed in order to move along a direction of the function there is a 
reduced occurrence of undershoot and overshoot. By integrating each push 
of the key 40a with an incremental change of the function, the user of the 
present invention has a sufficient amount of time in order to fine tune 
the subject function to a desired level. There is practically no chance 
for undershoot with the present invention since the user is provided an 
adequate amount of time (e.g., 1 second) in which to press the key 40a in 
order to increment the function. 
Even if there was an overshoot of a function, the overshoot would be 
minimal (likely only one increment) and the user would not only have to 
wait a very brief period of time (e.g., 1 second) in order to for the 
direction flag 100 to toggle the function direction to change. 
Although the present invention has been primarily described with respect to 
a single button contrast control, it will be appreciated that the present 
invention may be applied to a variety of functions in connection with a 
computing device. For example, the present invention could be used to 
control the volume or brightness of a computing device in much the same 
manner as was described above in controlling contrast of the display 14. 
Thus, it is to be understood any functions which conventionally require 
two directional buttons for bi-directionally incrementing the function and 
which can be accomplished with the single button control of the present 
invention, fall within the scope of the subject invention as recited in 
the claims. 
Further, although the preferred embodiment describes the single button 
control feature of the present invention to be used in conjunction with 
mobile devices, it will be appreciated that the single button control 
feature can be used with any device including standard desk top computers. 
The present invention includes all such equivalents and modifications, and 
is limited only by the scope of the following claims.