Abstract:
A wireless headset for use with a separate communications device, such as a cellular telephone, includes automatic on/off capabilities to maximize battery life. By detecting a user&#39;s interaction, such as picking up the headset or placing it upon the user&#39;s body, the wireless headset automatically transitions from an inactive state to an active state. Techniques for automatic headset enabling include but are not limited to motion sensors, attitude or position sensors, proximity sensors, and contact sensors. These techniques may be used individually or in any combination. An internal timer allows the wireless headset to return to its inactive state a defined interval after cessation of movement or removal of the wireless headset. Including an optional sleep state further optimizes battery life. In the sleep state, only a portion of the wireless headset circuitry is enabled. Rather than transitioning from inactive to active, the headset transitions from inactive to sleep. In sleep, the headset periodically monitors for a signal from the separate communications device. Upon detection of such a signal, the wireless headset transitions to its active state, thereby providing full functionality to the user.

Description:
FIELD OF THE INVENTION 
   The present invention relates to communications headsets such as might be used to interface with a cellular telephone and, in particular, to the design and operation of wireless headsets. 
   BACKGROUND OF THE INVENTION 
   Communications headsets provide a convenient interface to a variety of devices or base units, including telephones and computer systems. In particular, such headsets facilitate hands-free conversation using mobile terminals, such as cellular telephones. Of course, to impart practical advantages to hands-free conversation usage, such headsets must be convenient to wear and operate. Particularly, consumers desire small, lightweight headsets unencumbered by bulky and inconvenient cable attachments. Thus, communications headsets that are small and wireless are likely to enjoy widespread popularity, particularly if they are convenient to operate and own. Of course, the wireless headset must also provide for high-quality communications between it and the base unit. Several obstacles impede wireless headset designers in their efforts to provide consumers with small but reliable and convenient headsets. 
   One particular headset design problem is one of providing the user with a reliable mechanism for on/off control of the wireless headset. Continual reductions in the size of the elements comprising a typical wireless headset exacerbate the problem of locating a convenient and easy to operate on/off switch somewhere on the headset. Obviously, the relative size of the on-off switches used by designers must scale downward with the decreasing size of newer generation headsets. Small switches present a twofold problem. First, smaller switches are inherently more difficult to operate than larger ones. This problem is particularly acute for those with limited dexterity, poor eyesight, or compromised mental faculties. A second problem relates to the intrinsic shortcomings of inexpensive miniature switches. Namely, the second problem concerns overall switch reliability. Generally, the smaller switches are at once more fragile and less durable than their larger counterparts. Thus, inclusion of such miniaturized on-off switches compromises overall reliability of the wireless headset. 
   As the size of switches conveniently operable by the average user have a definite lower limit, the increasing miniaturization of wireless headsets leaves ever fewer convenient locations for incorporation of the on-off switch. Indeed, the design integrity of a wireless miniature headset may be compromised by the inclusion of any manually operated on-off switch. Such compromise results from the need to provide external access to the switch mechanism. This access generally requires an opening or break in the housing of the wireless headset. Such openings can compromise mechanical strength of the wireless headset housing and provide additional opportunities for the ingress of contaminants. 
   In keeping with the convenience afforded by their small size, miniature wireless headsets typically use internal batteries for operating power. Headset miniaturization places severe limitations on the physical size of batteries that may be included within the headset. Even with the significant energy densities afforded by newer battery technologies, these very small battery cells have significantly limited capacity. Because battery life is a key component of operator convenience, it is important that wireless headset design incorporates provisions maximizing battery life. A manually operated on-off switch works against this need to maximize battery life. For example, a user may forget to turn off the wireless headset after usage, thereby needlessly expending valuable battery life. 
   Accordingly, there remains a need for a wireless headset whose design and operation eliminates the need for bulky or hard to operate on-off switches, while maximizing battery life. The present invention satisfies these needs and others by providing a wireless headset capable of automatically turning on and off, based on user activity. 
   SUMMARY OF THE INVENTION 
   The present invention includes both a method and apparatus allowing a wireless headset to automatically control its operating state to minimize power consumption, thereby maximizing the life of its power source, such as a battery. The wireless headset serves as a communication accessory to a base unit, such as a cellular telephone. When not in use, the wireless headset reverts to an inactive state and draws essentially no power. A power control circuit imparts automatic enabling capability to the wireless headset. Preferably, the power control circuit employs a sensor responsive to a natural stimulus associated with a person preparing to use the wireless headset. The wireless headset may sense motion, physical orientation, or user proximity. Sensing techniques include but are not limited to micro-electro-mechanical-systems (MEMS), mercury switches, attitude switches, and IR or acoustic proximity sensors. In some embodiments, the wireless headset transitions from the inactive state to an active state in response to a user picking it up or mounting the wireless headset upon their head. 
   In a more sophisticated embodiment, the wireless headset may transition from the inactive state to a sleep state, based on user stimulus. In the sleep state, only a portion of the headset circuitry is enabled, thus conserving power. While in the sleep state, the wireless headset monitors for a signal from the base unit, and, when such a signal is received, it transitions from the sleep state to the active state. Further, once active, the wireless headset can continue to monitor for communications link activity. Thus, if communications with the base unit cease, the wireless headset can return to the sleep state and periodically check for resumed communications activity. A timer allows the wireless headset to automatically return to the inactive state subsequent to use. Cessation of movement or detected removal of the wireless headset from the user&#39;s head can indicate termination of use and trigger a timed power-down. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates an exemplary configuration of the wireless headset of the present invention. 
       FIG. 2A  is a simplified functional block diagram of the wireless headset in one exemplary embodiment of the present invention. 
       FIG. 2B  is a more detailed functional block diagram of a power control circuit in one exemplary embodiment of the present invention. 
       FIG. 3A  is a simplified functional block diagram of the wireless headset in a preferred embodiment of the present invention. 
       FIG. 3B  is a more detailed functional block diagram of the power control circuit in a preferred embodiment of the present invention. 
       FIG. 4A  is a simplified block diagram of the power control circuit with a MEMS sensor. 
       FIG. 4B  is a simplified block diagram of the power control circuit with a liquid-based switch. 
       FIG. 4C  is a simplified block diagram of the power control circuit with a contact switch. 
       FIG. 4D  is a simplified block diagram of the power control circuit with an IR sensor. 
       FIG. 4E  is a simplified block diagram of the power control circuit with a mechanical position switch. 
       FIG. 5  is a simplified functional block diagram of the sensor and power control circuit in an alternate embodiment of the present invention. 
       FIG. 6  is a state diagram of basic wireless headset operation in one embodiment of the present invention. 
       FIG. 7  is a state diagram of basic wireless headset operation in a preferred embodiment of the present invention. 
       FIG. 8  is a simplified block diagram for an exemplary embodiment of the present invention using an integrated controller for power control. 
       FIG. 9  is a simplified block diagram providing more detail regarding the integrated controller of  FIG. 8 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  illustrates one embodiment of the wireless headset  100  of the present invention. A user may advantageously use the wireless headset  100  for more convenient, hands-free interaction with the base unit  102 . As noted, the base unit  102  may be any type of device supporting interactive communications with a user. Commonly, the base unit  102  will be a communications device, such as a mobile terminal. The basic elements of the wireless headset  100  include a microphone pickup  120  for audio input, an earpiece  130  for audio output, a primary enclosure  110 , and a retaining member  140  with pad  150  to aid in securing the wireless headset  100  to the user&#39;s head. Notably,  FIG. 1  represents an exemplary configuration for the wireless headset  100 . The physical configuration shown in  FIG. 1  is a common configuration for wireless headsets. However, other configurations are possible. Those skilled in the art will appreciate that the physical configuration of the headset is not a material aspect of the invention. 
   Regardless of physical configuration,  FIG. 2A  illustrates one embodiment for the functional structure of the wireless headset  100  in accordance with one embodiment of the present invention. Wireless headset  100  includes a communications circuit  230  (also referred to as a headset circuit), a power control circuit  210 , a sensor  220 , and a power source  240 . 
   The communications circuit  230  provides wireless headset functionality, including audio input and output and wireless communications with the base unit  102 . The communications or headset circuit  230  includes a wireless communications interface  232  providing a wireless communications link for sending and receiving information to and from the base unit  102 . The wireless communications interface  232  includes at least a wireless receiver and wireless transmitter. Audio input received via microphone  236  is conditioned by the audio interface  234  and then processed by the communications interface  232  for transmittal to the base unit  102 . Audio information received from the base unit  102  is processed by the wireless communications interface  232  and then conditioned in the audio interface  234  for output to a user via speaker  238 . With reference to  FIG. 1A  or  1 B, the microphone  236  may be located in microphone pickup  120 , and speaker  238  may be located in earpiece  130 . 
   The power control circuit  210  selectively enables (activates) the communications circuit  230  in response to an output from sensor  220 . In some embodiments, the power control circuit  210  controls whether the communications circuit  230  is connected to the power source  240 . In other embodiments, the power control circuit  210  controls the amount of power consumed by communications circuit  230 . Conventionally, the power source  240  is a battery. 
   The communications circuit  230 , power control circuit  210 , sensor  220 , and power source  240 , may all be contained in the primary enclosure  110 , or may be distributed elsewhere in the structure of the wireless headset  100 . The specific packaging of the various elements comprising the wireless headset  100  is not critical to practicing the present invention. 
     FIG. 2B  provides more detail regarding the power control circuit  210  and sensor  220 . The interface between the power control circuit  210  and sensor  220  comprises one or more signal lines, and can include a power connection. The power control circuit  210  includes control logic  212  that is operatively associated with a switch  214 . In response to a sensor output signal, the control logic  212  causes switch  214  to turn on, thereby enabling or powering the communications circuit  230 . The power control circuit  210  includes a timer  218  that is reset by the control logic  212  based on the sensor output signal. The control logic  212  starts the timer  218  upon enabling the communications circuit  230 . Subsequent or continued assertion of the sensor output signal by the sensor  220  causes the control logic  212  to periodically reset the timer  218 , thereby preventing its expiration. As an alternative to periodic resetting, continued assertion of the sensor output signal may cause the power control circuit  210  to hold the timer  218  in reset. Absent such resetting, the timer  218  expires after timing a defined interval of time. Upon expiration of the timer  218 , the power control circuit  210  disables the communications circuit  230 . 
     FIG. 3A  illustrates a preferred embodiment for the wireless headset  100 . In  FIG. 3A , the power control circuit  210  independently enables the wireless communications interface  232  and audio interface  234 . Thus, select portions of communications circuit  230  may be enabled in response to the sensor output signal. Once the wireless communications interface  232  is enabled, it provides a signal, termed a “link active” signal, to the power control circuit  210  based on detecting a wireless signal received from the base unit  102 . Based on the assertion of the link active signal, the power control circuit  210  enables the audio interface  234 . 
     FIG. 3B  provides more functional details regarding the power control circuit  210  of  FIG. 3A . Again, the control logic  212  is responsive to a sensor output signal from sensor  220 . However, in response to the sensor output signal, the control logic  212  turns on switch  214  while switch  216  remains off, thereby enabling the wireless communications interface  232 . As with the previously discussed embodiment, power control circuit  210  includes the timer  218 . In a preferred embodiment, control logic  212  starts timer  218  upon enabling the wireless communications interface  232 , and resets timer  218  based on subsequent or continued assertion of the sensor output signal. If the wireless communications interface  232  asserts the link active signal, the control logic  212  turns on switch  216 , thereby enabling the audio interface  234 . If the timer  218  expires, the control logic  212  turns off switches  214  and  216 , thereby disabling the wireless communications interface  232  and the audio interface  234 . 
   Because the wireless headset  100  of the present invention automatically enables and disables its communication functions based on use, the sensor  220  may be based on a variety of technologies. In general, its purpose is to provide a signal responsive to a natural stimulus associated with use of the headset by a user. Movement or vibration of the wireless headset  100 , or placement of the wireless headset  100  upon the user&#39;s body indicates usage. Movement may be detected based on vibration or by sensing acceleration, such as with an accelerometer. Mechanical or liquid-based switches represent alternate mechanisms for sensing movement. In such switches, movement causes an electrical connection to be established between contact pairs. Further, the particular sensor  220  employed may be tuned or configured such that only stimulus consistent with actual use actuates the sensor, thus avoiding inadvertent or unintended enabling of the wireless headset  100 . In such configurations, the sensor  220  preferably employs output conditioning that prevents assertion of the sensor output signal for stimulus below a defined threshold. Alternatively, the power control circuit  210  may include such conditioning as part of its interface to the sensor  220 .  FIGS. 4A–4D  illustrate possible sensor embodiments. 
   In  FIG. 4A , the power control circuit  210  is operatively associated with a MEMS device, with the MEMS device functioning as the sensor  220 . Devices based on MEMS technology may be responsive to general vibration or motion, or may be configured to respond only to specific acceleration along defined axes. As MEMS devices may easily include output conditioning electronics, the sensitivity or responsiveness of the sensor  220  incorporating the MEMS device may be tailored such that the sensor output signal is asserted only for motion or vibration above a certain threshold. A typical MEMS employs modified microelectronics fabrication techniques and includes small mechanical elements responsive to movement or vibration, such as cantilever beams formed by selectively etching a silicon wafer. In a preferred embodiment of the present invention, sensor  220  includes a MEMS device simultaneously fulfilling the requirements of low power consumption, relative low-cost, and adequate signal discrimination. In this context, signal discrimination means that the sensor  220  is not prone to nuisance assertions of its sensor output signal caused by minute movement or vibration. Although the body of work associated with MEMS technology is quite comprehensive, significant insight into the basic structures and techniques of MEMS technology may be gained from U.S. Pat. No. 5,659,195 to Kaiser et al., U.S. Pat. No. 5,663,507 to Westervelt et al., and U.S. Pat. No. 5,76,480 to Pister, the disclosures of which are incorporated herein by reference. 
     FIG. 4B  illustrates the power control circuit  210  coupled to a liquid-based switch functioning as the sensor  220 . The sensor  220  may be a mercury-filled switch, or may employ other conductive liquids. Depending upon its configuration, the sensor  220 , implemented as a liquid-based switch, may function as a motion sensor or as an attitude sensor. As a motion sensor, the sensor  220  includes first and second contacts disposed in a manner such that motion of the contained liquid places the first and second contacts in electrical connection. As an attitude sensor, sensor  220  includes first and second contacts disposed in a manner such that one or more specific physical orientations of the wireless headset  100  causes the contained liquid in sensor  220  to place the first and second contacts in electrical connection. The power control circuit  210  connects to the first and second contacts of sensor  220 , and is responsive to the electrical connection completed by the contained liquid. 
     FIG. 4C  illustrates the power control circuit  210  coupled with a contact switch functioning as the sensor  220 . The contact switch includes a first and second contact connected to the power control circuit  210 , and connecting member  222  actuated when the user places the wireless headset  100  on their body. When actuated, the connecting member  222  places the first and second contacts of sensor  220  in electrical connection. Ideally, the sensor  220 , when configured as a contact sensor, is placed in the earpiece  130 , in the retaining member  140 , or in the retaining pad  150  shown in  FIG. 1B . Preferably, when sensor  220  is configured as a contact-based proximity sensor, the contacting element of sensor  220  is sealed in a manner that minimizes contaminant ingress. In some embodiments, the contact sensor may be actuated by the user resiliently expanding the retaining member  140  or other element of the wireless headset  100  for mounting upon their body. 
     FIG. 4D  illustrates the power control circuit  210  coupled with a proximity sensor  220  not based on mechanical actuation. The proximity sensor  220  may be an active or passive IR sensor, may be a resistive or other type of thermal sensor, or may be an acoustic sensor. As a proximity sensor, sensor  220  provides indication that a user has placed the wireless headset  100  upon their body. As such, any of the foregoing or other presence sensing techniques may be used to implement sensor  220 . Preferably, when configured as a proximity sensor, sensor  220  requires minimal power and provides a sensor output signal based on proximity to the user&#39;s body. Depending upon the sensing technology chosen, the control circuit  210  may be required to periodically stimulate sensor  220  to generate a detection response. 
     FIG. 4E  illustrates the power control circuit  210  coupled to an alternate type of attitude sensor  220 . In this embodiment, the attitude sensor  220  is a mechanical sensor that includes a contacting member  224  responsive to a physical orientation of the sensor  220 . In one or more physical orientations, the contacting member  224  does not electrically connect the first and second contacts of attitude sensor  220 . In one or more other physical orientations, the contacting member places the first and second contacts of attitude sensor  220  in electrical connection. The power control circuit  210  is configured to be responsive to this electrical connection. Contacting member  224  may be resiliently biased away from one or both contacts to ensure an open electrical connection between contacts when the headset is not oriented in a position indicative of use. 
     FIG. 5  illustrates yet another embodiment of the power control circuit  210  and associated sensor  220  in accordance with the present invention. Here, the sensor  220  in itself functions as a switch and provides a connection between the power source  240  and the power control circuit  210 . The power control circuit  210  also includes a switched power output from switch  214  that is commonly connected with the switched power output from sensor  220 . A blocking device  219 , such as a diode, allows the power control circuit  210  to determine if there is electrical continuity through sensor  220 . In the presence of such continuity, the control logic  212  turns on switch  214  thereby providing an independent power connection from the power source  240  to the communications circuit  230 . As before, the power control circuit  210  includes the timer  218  that is started when switch  214  is turned on, and restarted based on electrical continuity through sensor  220 . If the timer  218  expires due to an absence of electrical continuity through sensor  220 , the control logic  212  disables the communications circuit  230 . 
   Note that the foregoing diagrams illustrate various configurations for the present invention, with these configurations allowing the wireless headset  100  to automatically enable and disable select portions of its electronic circuitry based on user stimulus. Enabling and disabling may constitute physical connection and disconnection of power between the power source  240  and the communications or headset circuit  230 , or may simply represent the assertion and de-assertion of specific enabling signals. Thus, the foregoing diagrams should not be construed as limiting in any way regarding the specific circuit implementation of the wireless headset  100 .  FIGS. 2–5  illustrate functional diagrams and these various functions may have corresponding separate circuit elements, or may be included in integrated fashion in one or more devices. For example, a microprocessor in a sleep or halt mode may be directly connected to a battery and configured to wake up in response to an input from the sensor  220 . Thus, the microprocessor could serve as the power control circuit  210 , as well as providing functions related to the communications interface  232  and audio interface  234 . 
     FIGS. 8 and 9 , in particular, illustrate an exemplary embodiment of the present invention wherein an integrated controller provides the functionality of the power control circuit  210 . In  FIG. 8 , the power control circuit  210  includes an integrated controller  300 . The integrated controller  300  provides power control functionality associated with the timer  218 , switches  214  and  216 , and control logic  212 . In this embodiment, the controller  300  provides both power and control/signal interconnections for the wireless communications interface  232  and audio interface  234 . The controller  300  independently enables the wireless communications interface  232  and audio interface  234  in response to the sensor output signal from sensor  220 . As with other embodiments, the controller  300  may enable both the wireless communication interface  232  and audio interface  234  in response to the sensor output signal, or may only enable the wireless communications interface  232 , or a portion thereof. In this latter, case, the controller  300  enables the audio interface  234  in response to receiving the link signal from the enabled portion of the wireless communications interface  232 . 
     FIG. 9  provides more detail regarding the controller  300  shown in  FIG. 8 . A main power controller  310  provides power/control outputs to power controllers  330  and  340 , which, in turn, provide power control outputs to the wireless communications interface  232  and audio interface  234 , respectively. The main power controller  310  additionally interfaces with and provides power to a functional controller  350  and a sensor controller  320 . The functional controller  350  provides signal and control interfaces with both the wireless communications interface  232  and the audio interface  234 . In an exemplary embodiment, the main power controller initially enables only the sensor controller  320 . 
   Then, in response to the sensor output signal, the main controller  310  enables power controller  330  at least a portion of the functional controller  350 . In response, power controller  330  enables at least a portion of the wireless communications interface  232 . Then, in response to receiving the link signal from the wireless communications interface  232 —the link signal may be received via the functional controller  350 —the main power controller  310  enables the power controller  340  associated with the audio interface  234 . The power controllers  330  and  340  may comprise FET switches combined with control logic responsive to control signals asserted by the main power controller  310 , the functional controller  350 , and/or the wireless communications interface  232 . 
   The specific configuration of the integrated controller  300  illustrated in  FIGS. 8 and 9  will depend upon particular design requirements and available system resources. The integrated controller  300  may be a microprocessor, ASIC, or other programmable logic device and, as such, the features and capabilities of the selected architecture will determine the specific implementation for such embodiments. 
     FIGS. 6 and 7  illustrate operation of the wireless headset  100 .  FIG. 6  is a state diagram for one exemplary embodiment of the present invention. When the wireless headset  100  is not in use, it automatically enters an inactive state ( 610 ). As explained, this inactive state may constitute disconnecting the communications circuit  230  from the power source  240 , or may simply represent placing the communications circuit  230  in a non-functional, low-power condition. Absent user stimulus, such as motion of the wireless headset  100  or placement of the wireless headset  100  upon the user&#39;s body, the wireless headset  100  remains in the inactive state ( 610 ). 
   In response to user stimulus, as detected by sensor  220 , the power control circuit  210  enables the communications circuit  230 , with this enabling representing a transition from the inactive state to an active state ( 620 ). Upon entering the active state, the power control circuit  210  initializes and starts the timer  218 . The timer  218  incrementally counts from a starting value to an ending value, with the progression from starting to ending values representing a defined interval of time. Upon expiration of the timer  218 , the power control circuit  210  disables the communications circuit  230 . This interval of time may be preprogrammed to a convenient value, or may be selectable based on input from the base unit  102 . For example, a timeout interval of five minutes may provide a reasonable compromise between user convenience and battery life. While in the active state ( 620 ), the power control circuit  210  resets the timer  218  based on the reassertion or continued assertion of the sensor output signal from sensor  220 . Such resetting prevents expiration of the timer  218  and, as such, causes the power control circuit  210  to leave the communications or headset circuit  230  enabled. Thus, the power control circuit  210  is designed to leave the wireless headset  100  in the active state ( 620 ) while the wireless headset is in use by a user. Absent user stimulus, the timer  218  of power control circuit  210  expires, thereby causing the wireless headset  100  to transition from the active state ( 620 ) to the inactive state ( 610 ) based on the power control circuit  210  disabling the communications circuit  230 . 
     FIG. 7  is a state diagram for a preferred embodiment of the present invention. Operation of the wireless headset  100  illustrated in  FIG. 7  is distinguished from that shown in  FIG. 6  by inclusion of an additional state, denoted as the sleep state ( 720 ). Inclusion of the sleep state provides an additional opportunity to control the power consumption of wireless headset  100  based on specific operating conditions. As before, the wireless headset  100  remains in the inactive state ( 710 ) absent user stimulus. Upon detecting user stimulus, the wireless headset  100  transitions from the inactive state ( 710 ) to the sleep state ( 720 ). In this state, the power control circuit  210  enables only a portion of the communications circuit  230 . Specifically, the power control circuit  210  enables the wireless communications interface  232  or a portion thereof. Then, using a signal output from the wireless communications interface  232 , the power control circuit  210  determines if the base unit  102  is active, or if the base unit  102  is attempting to communicate with the wireless headset  100 . In some embodiments, the wireless headset  100  infers activity by detecting, via its wireless communications interface, a carrier signal from the base unit  102 . In other embodiments, the wireless headset detects activity based on receiving a “wake-up” signal from the base unit  102 . Note that monitoring for the base unit carrier signal may be performed continuously by the wireless headset  100  while in the sleep state, or may be performed periodically; thereby further reducing sleep state power consumption. For periodic carrier monitoring, the wireless headset  100  may employ an exemplary monitoring interval of 0.5 seconds. 
   Upon detecting the carrier signal or wake-up signal from the base unit  102 , as indicated by the link signal shown in  FIG. 7 , the wireless headset  100  transitions from the sleep state ( 720 ) to the active state ( 730 ). To further reduce power consumption, the wireless headset  100  may only monitor for the external signal on a periodic basis. If the wireless headset  100  is configured to monitor for the external signal on a periodic basis and the base unit  102  is configured to emit a periodic wake-up signal, the periodic monitoring of the wireless headset  100  is set such that its monitoring frequency is not an integer multiple of the wake-up signal frequency. Upon causing the wireless headset  100  to transition from the inactive state ( 710 ) to the sleep state ( 720 ), the power control circuit  210  initializes and starts the timer  218 . 
   While in the sleep state ( 720 ), subsequent or continued assertion of the sensor output signal from the sensor  220  causes the power control circuit  210  to reset its timer  218 . Absent such user stimulus, the timer  218  expires and the power control circuit  210  disables the communications circuit  230 . After transitioning from the sleep state ( 720 ) to the active state ( 730 ), based on detection of the signal from the base unit  102 , the power control circuit  210  continues resetting its timer  218  based on user stimulus, as done in the sleep state ( 720 ). Thus, continued user stimulus causes the power control circuit  210  to leave the wireless headset  100  fully functional in the active state ( 730 ). 
   The present invention provides methods and apparatus allowing the wireless headset  100  to conveniently transition from a non-functional inactive state to a fully functional active state, based on its detection of certain user stimulus. In a preferred embodiment, the wireless headset  100  transitions from the inactive state to the intermediate sleep state, thereby conserving power. Upon detection of the carrier or the wake-up signal from the base unit  102 , the wireless headset  100  transitions from the sleep state to the fully functional active state. The wireless headset  100  includes a sensor  220  for detecting the user stimulus. As the sensor  220  may be a motion sensor, a vibration sensor, an attitude sensor, or a proximity sensor, the specific user stimulus may include the user moving and/or placing the wireless headset  100  upon their body. The operation of the wireless headset  100  in accordance with the present invention admits tremendous flexibility with respect to implementation. As noted, many different circuit implementations may provide the inventive features of the present invention. These implementations may include hardware and software, and can reflect varying degrees of integration between the functional circuit blocks discussed. Indeed, all such variations for providing a wireless headset  100  that automatically controls its power consumption or operating state based on detection of a user stimulus are within the scope of the present invention. 
   The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.