Patent Publication Number: US-11665462-B1

Title: Headband identification for a headphone system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 63/079,397, filed Sep. 16, 2020, the disclosure of which is incorporated by reference. 
    
    
     BACKGROUND 
     This disclosure relates generally to headphone systems and in particular to automatic identification of a headband in a headphone system. 
     A “personal audio device” refers to a device that produces sound to be heard by an individual user while limiting the audibility of that sound in an environment around the user. Headphones are one common type of personal audio device, which remain popular in part because they can provide superior acoustic performance as compared to more compact earbud systems. Headphones generally include one or two audio-producing earpieces (also referred to as “ear cups”) that are designed to be worn over the ear or on the ear. The ear cups are connected to a headband, which can help to hold the ear cups in place and can also provide an electrical connection between the ear cups. The ear cups are designed to be worn such that an audio-generating speaker contained in each ear cup directs sound toward an ear of the wearer. A cushion made of compliant material is typically provided around a peripheral portion of the ear cup in order to provide spacing between the speaker and the user&#39;s ear and to provide user comfort while wearing the headphones. The cushion may also provide sound insulation, preventing sound generated by the ear cups from leaking into the environment and/or preventing external sound from reaching the user&#39;s ears. 
     Headphones are often used as accessories to a “host” device that can provide audio to the headphones. For example, headphones may be communicably coupled to a host device such as a mobile phone, tablet computer, laptop computer, gaming device, TV receiver, stereo system or any other device that can deliver an audio signal to the headphones via a wired or wireless communication channel. 
     SUMMARY 
     Certain embodiments of the present invention relate to headphone systems or other personal audio devices in which the earpieces (e.g., ear cups) are detachably connected to a headband that provides power and data connections between the ear cups. It is assumed that a user can detach one headband from the ear cups and replace it with a different type of headband. Different types of headbands can be distinguishable based on appearance (e.g., color, width, finish) and/or functionality (e.g., amount of cushioning, clamping force, size, etc.). In a headphone system with interchangeable headbands of different types, it may be desirable to identify the attached headband, e.g., to enable appropriate modifications to a user interface of a host device and/or to audio signals provided to or by the headphones. 
     Accordingly, some embodiments of the present invention relate to headbands for headphone systems. The headband can include a body, which can be elongate and arched to fit over a user&#39;s head. A connector can be disposed at each end of the body. For instance, each connector can be a plug (or insert) connector that is adapted to fit into a complementary receptacle connector of an ear cup. Within the body of the headband, power and data lines (e.g., wires) can be coupled between the connectors at either end to enable communication between the two ear cups. In addition, a headband identification circuit can be disposed within the body of the headband and coupled to at least one of the data lines. The headband identification circuit can be configured to generate a pulse sequence on the data line in response to ear cups becoming connected to both connectors. The particular pulse sequence can be associated with a specific type of headband, so that headband identification circuits in headbands of different types generate different pulse sequences. Receiver circuitry in one of the ear cups can detect the pulse sequence and determine a headband identifier based on the pulse sequence. In some embodiments, the ear cup that determines the headband identifier can communicate the headband identifier to a host device with which the headphone system is communicably coupled and/or to the other ear cup. 
     The following detailed description, together with the accompanying drawings, will provide a better understanding of the nature and advantages of the claimed invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows an example of a headphone system according to some embodiments. 
         FIG.  2    is a simplified schematic diagram showing electrical connectivity of a headphone system according to some embodiments. 
         FIGS.  3 A and  3 B  show additional details of a unidirectional data coupling for ear cups connected by a headband according to some embodiments. 
         FIG.  4    shows a simplified schematic diagram of a headband ID circuit according to some embodiments. 
         FIGS.  5  and  6    are timing diagrams showing the state of various signals in an ear cup according to some embodiments. 
         FIG.  7    shows a simplified schematic diagram of another headband ID circuit according to some embodiments. 
         FIG.  8    shows a simplified schematic diagram of a circuit for an ear cup according to some embodiments. 
         FIGS.  9 A and  9 B  illustrate reversibility of a headband according to some embodiments 
         FIGS.  10 A and  10 B  show bottom and top views of a printed circuit board that incorporates a headband ID circuit according to some embodiments. 
         FIGS.  11 A and  11 B  show an assembled view and an exploded view of a connector assembly according to some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Certain embodiments of the present invention relate to headphone systems or other personal audio devices in which the earpieces (e.g., ear cups) are detachably connected to a headband that provides power and data connections between the ear cups. It is assumed that a user can detach one headband from the ear cups and replace it with a different type of headband. Different types of headbands can be distinguishable based on appearance (e.g., color, width, finish) and/or functionality (e.g., amount of cushioning, clamping force, size, etc.). In a headphone system with interchangeable headbands of different types, it may be desirable to identify the attached headband, e.g., to enable appropriate modifications to a user interface of a host device and/or to audio signals provided to or by the headphones. 
       FIG.  1    shows an example of a headphone system  100  according to some embodiments. Headphone system  100  includes a pair of earpieces (also referred to as ear cups)  102  and a headband  104  that mechanically and electrically connects ear cups  102 . Ear cups  102  can be made of rigid materials such as rigid plastic and/or metal. Ear cups  102  can be designed and shaped to fit on top of or around the pinnae of the user&#39;s ears, covering the concha cavum, and the portion of each ear cup  102  that rests against a user&#39;s head can be covered by a cushion  103  to provide increased comfort and/or improved acoustic performance. Ear cups  102  can incorporate one or more speakers to produce sound directed toward the user&#39;s ears, control electronics to operate the speakers, a signal interface to receive audio signals in digital or analog format, one or more user input controls (e.g., one or more touch sensitive areas on a surface of one or both of ear cups  102 ), and other components that can be of generally conventional design. Cushions  103  can be formed with a core of foam or other compressible material surrounded by a compliant structural layer that helps to define a shape of a periphery of cushions  103  without imparting rigidity. One or more additional textile layers can be applied if desired, e.g., for user comfort, durability, and/or esthetic appearance. In some embodiments, cushions  103  can be interchangeable by a user. Headband  104  can be connected between ear cups  102 . Headband  104  can have an elongate, arch-shaped body designed to fit over the top of a user&#39;s head. The body of headband  104  can be made of a resilient material or otherwise designed to exert a compression force that pulls ear cups  102  toward each other, helping to hold ear cups  102  in position on a user&#39;s head. Portions of the body of headband  104  (e.g., a surface proximate to a user&#39;s head) can include padding as desired. 
     Headband  104  can be detachably attached to ear cups  102 . For example, a connector assembly  106  can be disposed at each end of the body of headband  104 . Each connector assembly  106  can include a plug (or insert) connector that fits into a corresponding receptacle connector on ear cup  102 . Connector assemblies  106  can provide mechanical and electrical coupling between headband  104  and ear cups  102 . For example, as shown in inset  130 , each connector assembly  106  can include exposed electrical contacts  108  that can make contact with corresponding contacts (not shown) in the receptacle connector in ear cup  102 . Electrical contacts  108  can be connected to data and/or power cables (or wires) that run the length of headband  104 , thereby providing electrical connections between the two ear cups  102 . In some embodiments, the two connector assemblies  106  of headband  104  can be identical, and either end of headband  104  can be connected to either of a pair of ear cups  102 . Specific examples of connector insert assemblies  106  and complementary receptacle connector assemblies that can be used to connect headband  104  to ear cups  102  are described in U.S. patent application Ser. No. 17/023,013, filed Sep. 16, 2020, which is incorporated herein by reference. It will be appreciated that other connector assemblies can also be used. 
     For purposes of the present disclosure, it is assumed that multiple types of headbands  104  exist that are compatible with the same ear cups  102 . In various embodiments, different types of headbands  104  may be distinct from each other in size, color, materials, and/or esthetic other attributes. In some embodiments, in addition to or instead of esthetic distinctions, different types of headbands  104  may have different effects on audio performance (e.g., the amount of clamping force exerted by a given headband  104  may affect the acoustic properties of ear cups  102 ), battery life (e.g., due to differences in the length of power and/or data cables within a given headband), and/or other functional characteristics of headphone system  100 . In some embodiments, different types of headbands  104  can be user-interchangeable; that is, a user may attach different headbands  104  of different types to the same pair of ear cups  102  at different times, e.g., by connecting a desired headband  104  to ear cups  102 . To facilitate identification of which headband  104  is currently attached to ear cups  102 , each headband  104  can include a headband identification circuit  110  that encodes identification data indicating the type of headband. For instance, as shown in  FIG.  1   , headband identification circuit  110  can be disposed in connector assembly  106  at one end of headband  104 . When headband  104  becomes connected to ear cups  102 , headband identification circuit  110  can send identification data to one (or both) of ear cups  102 , for example by generating pulses on a data line that runs between the connector assemblies  106  at either end of headband  104 . The identification data can be read by circuitry within one (or both) of ear cups  102 , allowing the behavior of headphone system  100  to automatically adapt based on the particular type of headband  104  that is attached at any given time. Specific examples are described below. 
     In some embodiments, headphone system  100  can operate as an accessory to a host device  150 . Host device  150  can be, for example, a smart phone, a tablet computer, a laptop computer, a desktop computer, a wearable device (e.g., a smart watch), a game console or portable gaming device, or any other electronic device that provides audio output. Headphone system  100  can connect to host device  150  via a wired or wireless communication channel that supports transfer of audio data (in digital and/or analog formats) from the host device to headphone system  100 . In some embodiments, the communication channel can be bidirectional, allowing headphone system  100  to communicate information to host device  150 . For example, headphone system  100  can communicate headband identification data read from headband identification circuit  110  to host device  150 , and host device  150  can modify its behavior based on the headband identification data received from headphone system  100 . Specific examples are described below. It should be understood that information other than audio signals and headband identification data can also be communicated between headphone system  100  and host device  150 . For example, headphone system  100  can provide a user input interface that includes, e.g., tactile controls (buttons, touch-sensitive surfaces, or the like) and/or a microphone for voice input, and headphone system  100  can communicate user input to host device  150 . Host device  150  can be of conventional or other design, and presence of a host device is not required. 
     Examples of headband identification circuits will now be described. For purposes of description, it is assumed that headband identification data can be encoded as a numerical parameter value, with different parameter values corresponding to different headband types. For example, if headbands are distinguished by color, a parameter value of 1 can map to black, 2 to red, 3 to blue, 4 to white, and so on. If headbands are distinguished by color and width, a parameter value of 1 can map to a narrow black headband, 2 to a wide black headband, 3 to a narrow red headband, and so on. Any mapping of parameter values to headband types cam be defined. In various embodiments, any number of distinct parameter values can be supported, depending on the particular implementation of the headband identification circuit. During manufacture, a value of the identification parameter appropriate to a particular headband can be encoded or stored in the headband identification circuit for that headband. It is assumed that the parameter value does not change after initial encoding or storing; hence, the identification parameter value may be referred to as being “predetermined.” 
       FIG.  2    is a simplified schematic diagram showing electrical connectivity of a headphone system  200  according to some embodiments. Headphone system  200  can be, e.g., an implementation of headphone system  100  of  FIG.  1   . Headphone system  200  includes a primary ear cup  202   a  and a secondary ear cup  202   b  (e.g., implementing ear cups  102  of  FIG.  1   ). It is assumed that ear cups are made and distributed in pairs, each pair including a primary ear cup  202   a  and a secondary ear cup  202   b . One or both of primary ear cup  202   a  and secondary ear cup  202   b  can include a battery (or other power source) and associated circuitry (e.g., for charging the battery), and one or both of primary ear cup  202   a  and secondary ear cup  202   b  can include a microcontroller unit (e.g., MCU  244 ) and communication interface circuitry to communicate with a host device such as host device  150  of  FIG.  1   . The components of primary and secondary ear cups  202   a ,  202   b  can be of conventional or other design, and a detailed description is omitted. Primary ear cup  202   a  and secondary ear cup  202   b  can each include a receptacle connector  230   a ,  230   b  that can be connected to headband  204 , thereby attaching headband  204  to primary ear cup  202   a  and secondary ear cup  202   b . In  FIG.  2   , primary ear cup  202   a  is shown as detached from headband  204  while secondary ear cup  202   b  is shown as attached to headband  204 . 
     Headband  204  (e.g., implementing headband  104  of  FIG.  1   ) can provide electrical connectivity between primary ear cup  202   a  and secondary ear cup  202   b . For example, headband  204  can include power lines  222  and data lines  224 . Power lines  222  and data lines  224  can include elongate electrically conductive structures that are insulated from other electrically conductive structures, having ends that can be electrically connected to other conductive structures. For example, each line can be a single-stranded or multi-stranded copper wire wrapped in a sleeve of insulating material. In some embodiments, power lines  222  and data lines  224  can support standard USB signaling protocols between primary ear cup  202   a  and secondary ear cup  202   b . For instance, power lines  222  can provide DC power and can include a ground line and a positive (e.g., +5V DC) line, while data lines  224  can include a differential pair of data lines (D+/D−) supporting USB data communication. In some embodiments, two differential pairs of data lines  224  can be provided, with one pair of data lines providing a path for transmitting data from primary ear cup  202   a  to secondary ear cup  202   b  and the other pair of data lines providing a path for transmitting data from secondary ear cup  202   b  to primary ear cup  202   a . Each end of power lines  222  and data lines  224  can be coupled into a connector  206  such that exposed contacts  208  include contacts that are electrically connected to each of power lines  222  and data lines  224 . It should be understood that connectors  206  can be identical to each other, and accordingly receptacle connectors  230   a ,  230   b  can also be identical to each other. Thus, either instance of connector  206  can be interchangeably inserted into either of receptacle connectors  230   a ,  230   b.    
     Headband  204  can include a headband identification (also referred to as “headband ID” or “HBID”) circuit  210  that is connected to one or more of data lines  224 . HBID circuit  210  can include, for example, an application-specific integrated circuit (ASIC) and supporting circuitry. In operation, the ASIC can generate a predefined series of pulses on one or more of data lines  224 . The predefined series of pulses can represent a value of a headband identification parameter. Pulses on one or more of data lines  224  can be detected by receiver circuitry located in one or both of ear cups  202   a ,  202   b , enabling one or both of ear cups  202   a ,  202   b  to read the value of the identification parameter. In some embodiments, HBID circuit  210  can be configured such that, in response to both of primary ear cup  202   a  and secondary ear cup  202   b  becoming attached to headband  204 , HBID circuit  210  enters an active state in which the predefined series of pulses is generated, after which HBID circuit  210  transitions to a “dormant” (low-power) state, in which HBID circuit  210  consumes little or no power and does not affect data communication between primary ear cup  202   a  and secondary ear cup  202   b . HBID circuit  210  can remain in the dormant state until a detachment followed by subsequent reattachment occurs. Examples of specific implementations of HBID circuit  210  are described below. In these and other embodiments, HBID circuit  210  can operate using the same electrical paths that are used for data communication between primary ear cup  202   a  and secondary ear cup  202   b ; no additional contacts or signal paths are required. 
     The pulse sequence generated by HBID circuit  210  can encode an identification parameter value using various techniques. In some embodiments, the parameter value can be encoded as a number of pulses, and headband identification can be based on pulse counting. For instance, HBID circuit  210  can be configured to generate a specific number of pulses associated with the headband type of headband  204 , and secondary ear cup  202   b  (or primary ear cup  202   a ) can count the pulses to determine an identification parameter (e.g., a numerical value). In some embodiments, the mapping of pulse counts to an identification parameter can allow for error in counting (e.g., due to false negatives or false positives during pulse detection), providing more robust identification. For example, an identification parameter value of N (where N is a positive integer) can be indicated by a number 8N of pulses, and the parameter value N can be mapped to a detected count of 8N, 8N+1, or 8N−1 pulses. Thus, for example, if 7, 8, or 9 pulses are counted, then N=1; if 15, 16, or 17 pulses are counted, then N=2, and so on. Where pulse counting is used, the number of distinct identifiers may be limited by the maximum number of pulses that can be sent (which in turn can depend on design choices such as the available time to send pulses and the rate at which pulses can be generated) and the degree of robustness desired. Other schemes for encoding a parameter value, including encoding schemes based on pulse duration in addition to or instead of number of pulses, can also be employed depending on the particular implementation of HBID circuit  210 . 
       FIGS.  3 A and  3 B  are schematic diagrams showing additional details of a unidirectional data coupling for ear cups connected by a headband according to some embodiments.  FIG.  3 A  shows a transmitter data coupling for primary ear cup  202   a , and  FIG.  3 B  shows a receiver data coupling for secondary ear cup  202   b . These couplings enable data to be transmitted from primary ear cup  202   a  to secondary ear cup  202   b . As described below, headband identification pulses can be injected into this data path by HBID circuit  210 . As shown in  FIG.  3 A , primary ear cup  202   a  includes a USB transmit switch  340   a  that can receive input signals on lines  342   a . Such input signals can be generated, e.g., by a microcontroller or other component(s) of primary ear cup  202   a  and can represent any data or information that is to be transmitted to secondary ear cup  202   b . USB transmit switch  340   a  is inductively coupled to differential data contacts  332   a ,  334   a , which can be contacts in receptacle connector  230   a . Similarly, as shown in  FIG.  3 B , secondary ear cup  202   b  includes a USB receive switch  340   b  that is inductively coupled to differential data contacts  332   b ,  334   b , which can be contacts in receptacle connector  230   b . As shown in  FIG.  2   , headband  204  can be connected between receptacle connector  230   a  and receptacle connector  230   b  and can include a pair of data lines  224  that couple data contact  332   a  to data contact  332   b  and data contact  334   a  to data contact  334   b . USB receive switch  340   b  can be coupled to a UART circuit  342 , which decodes the received signals and delivers them to a microcontroller unit (MCU)  334 . 
     In operation, USB transmit switch  340   a  in primary ear cup  202   a  can receive input signals  342   a  and can generate a voltage differential between data contacts  332   a ,  334   a  responsive to input signals  342   a . The voltage differential can propagate (via headband  204  connected between receptacle connectors  230   a  and  230   b  as shown in  FIG.  2   ) to data contacts  332   b ,  334   b  of secondary ear cup  202   b . USB receive switch  340   b  can sense the voltage differential and generate a digital data signal using circuit  342 , which is delivered to MCU  344 . The circuitry shown in  FIGS.  3 A and  3 B  can be of generally conventional design and operation. Those skilled in the art will be familiar with numerous techniques for transmitting data using a differential pair of signal paths, and any such techniques can be used in connection with headband identification as described herein. 
     While  FIGS.  3 A and  3 B  show a unidirectional signaling path, it should be understood that bidirectional communication between ear cups  202   a ,  202   b  can be supported. For instance, each of ear cups  202   a  can include both a USB transmit switch and a USB receive switch (and associated circuitry), each coupled to a pair of data contacts, and headband  204  can include two pairs of data lines, one for each direction. In embodiments shown herein, the headband ID circuit is coupled to the data lines connecting the USB transmit switch of the primary ear cup to the USB receive switch of the secondary ear cup (such lines can be said to carry or transmit data from the primary ear cup to the secondary ear cup). Those skilled in the art will appreciate that a headband ID circuit can instead be connected to data lines connecting a USB transmit switch of the secondary ear cup to a USB receive switch of the primary ear cup, and either ear cup can be used to receive headband identifying data from a headband ID circuit. In some embodiments, a headband ID circuit can be connected to the data lines in both directions, and both ear cups can receive headband identifying data. Thus, while the present disclosure may describe particular components or operations as being implemented in a primary (or secondary) ear cup, those skilled in the art will appreciate that any ear cup can be configured to receive headband identification information in the manner described herein, regardless of any other features or capabilities the ear cup may include. 
     As described above, the ear cups can rely on differential voltage across a pair of data lines to communicate data. A “pulse” can be any event that results in a voltage difference across the pair of data lines that is detectable by the receiving ear cup. Examples of headband ID circuits that can generate pulses on a pair of data lines will now be described.  FIG.  4    shows a simplified schematic diagram of a headband ID circuit  410  coupled to a differential pair of data lines  422   a ,  422   b  according to some embodiments. Headband ID circuit  410  can be an implementation of HBID circuit  210  of  FIG.  2   . Data lines  422   a ,  422   b  can be coupled between data contacts  334   a ,  332   a  in primary ear cup  202   a  and data contacts  334   b ,  332   b  in secondary ear cup  202   b . For instance, data lines  422   a ,  422   b  can be a subset (or all) of data lines  224  running the length of headband  204  and coupled to connectors  206  as shown in  FIG.  2   . 
     Headband ID circuit  410  includes an ASIC  412 . ASIC  412  can include, e.g., an oscillator that oscillates at a frequency in the kilohertz or megahertz range (e.g., ˜2 MHz). The oscillator can be coupled to digital logic internal to ASIC  412  that can generate a pulsed output on output path  413 . For example, ASIC  412  can be programmed to generate a specific (invariant) number N of pulses, where N is the predetermined identification parameter value for a particular type of headband. In some embodiments, ASIC  412  can also include timer logic that imposes a fixed delay between when ASIC  412  is powered on and when ASIC  412  begins generating pulses on output path  413 . Output path  413  provides a voltage at a base terminal of a transistor  414  that has a collector terminal coupled to one of data lines  422  and emitter terminal coupled to ground. In some embodiments, transistor  414  can be an NPN-type bipolar junction transistor, which has reduced sensitivity to electrostatic discharge events as compared to a MOSFET; however, other types of transistors (including, e.g., NMOS or other MOSFETs) can be substituted. ASIC  412  can draw operating power (VDD) from a capacitor  416  that is coupled to data lines  422   a ,  422   b  via resistors  418 . Diodes  420  can provide transient voltage suppression. 
     In operation, when both ends of data lines  422   a ,  422   b  become connected to ear cups, primary ear cup  202   a  (or whichever ear cup uses data lines  422   a ,  422   b  for transmitting data) can drive both of data lines  422   a ,  422   b  to a high-Z state, and capacitor  416  can begin to charge. Once capacitor  416  has charged to a sufficient level, ASIC  412  can enter an active state and starts the timer logic. The timer logic can impose a fixed delay (e.g., 16 ms), after which ASIC  412  begins generating pulses on output path  413 . These pulses create transient voltage reductions on data line  422   a  (but not on data line  422   b ) due to the operation of transistor  414 . This creates a differential pulsed signal that can be sensed by secondary ear cup  202   b  (or whichever ear cup uses data lines  422   a ,  422   b  for receiving data), which can detect and count the pulses, thereby determining the identification parameter. 
     Operation of HBID circuit  410  is further illustrated in  FIGS.  5  and  6   , which are timing diagrams showing the state of various signals according to some embodiments. For purposes of description, it is assumed that HBID circuit  410  couples to the data lines that transmit data from primary ear cup  202   a  to secondary ear cup  202   b .  FIG.  5    shows the behavior of a secondary ear cup (e.g., secondary ear cup  202   b  of  FIG.  2   ) when no primary cup is attached. Plot  502  represents an internal voltage (“vddmain”) that secondary ear cup  202   b  can generate. Plot  504  represents a connection detect (“CONDET”) supply voltage that secondary ear cup  202   b  can receive from primary ear cup  202   a . HBID supply plot  506  represents a voltage input to ASIC  412  of HBID circuit  410 , e.g., from capacitor  416 ). Plot  508  represents signals received by secondary ear cup  202   b  via data lines  422   a ,  422   b , and plot  510  represents signals transmitted by secondary ear cup  202   b  to primary ear cup  202   a.    
     As shown in plot  502 , secondary ear cup  202   b  can periodically generate a vddmain pulse  512  having a fixed “default” duration (3 ms in this example). If there is no response from a primary ear cup (which, as described below, would appear in CONDET supply plot  504  and received data plot  508 ) within the default duration, secondary ear cup  202   b  can stop generating vddmain, thereby conserving power. HBID supply plot  506  shows the voltage input to ASIC  412  of headband ID circuit  410 . The HBID supply voltage can rise to the point  514  where ASIC  412  becomes active and starts its timer (as indicated at  516 ) preparatory to generating pulses, but once vddmain drops to zero the HBID supply voltage decreases again, reaching a power-off threshold  518  before the timer expires. Consequently, as shown in plot  508 , no headband ID pulses are generated on the transmit line from the (absent) primary ear cup to the secondary ear cup. In some embodiments, secondary ear cup  202   b  can actively drain capacitor  416  of headband ID circuit  410  after vddmain drops to zero, which can prevent pulses from being generated and can also reset ASIC  412 . As shown in  FIG.  5   , as long as no primary ear cup is attached, secondary ear cup  202   b  can periodically generate vddmain pulses, e.g., a 3 ms pulse can be generated every 300 ms. 
       FIG.  6    shows a corresponding timing diagram to  FIG.  5   , for a case where primary ear cup  202   a  becomes attached (via headband  204 ). As shown in plot  602 , secondary ear cup  202   b  can generate a voltage (vddmain) pulse  612  and receive a response within the default duration of the pulse (3 ms in this example). As shown in plot  604 , the response can include, e.g., a connection-detect (“CONDET”) supply signal being received at  614 . The CONDET supply signal can include, e.g., power received on a power path connecting primary ear cup  202   a  to secondary ear cup  202   b . In addition, as shown in plot  608 , primary ear cup  202   a  can transmit a series of pulses  616  indicating connection detected. After transmitting CONDET pulses  616 , primary ear cup  202   a  can drive its data transmit lines to high-impedance in preparation for headband ID. These events can occur within the default duration (e.g., 3 ms) of the initial vddmain pulse, and in response secondary ear cup  202   b  maintains the voltage level vddmain after 3 ms, as shown in plot  602 . 
     As in the case of  FIG.  5   , vddmain pulse  612  results in the HBID supply voltage input to ASIC  412  of headband ID circuit  410  beginning to rise, as shown in plot  606 , and voltage can rise to the point  616  where ASIC  412  becomes active and starts its timer (as indicated at  618 ). In this case, because vddmain does not cut off, the voltage input (plot  606 ) remains high, and the timer logic in ASIC  412  can count its full duration (16 ms in this example). When the timer elapses, ASIC  412  can generate headband identification pulses  620  on the primary-to-secondary data lines, as shown in plot  608 . Headband identification pulses  620  can be received and decoded by secondary ear cup  202   b . Once the headband identification pulses have stopped, headband ID circuit  410  can transition ASIC  412  into a low-power state, which can include e.g., turning off the oscillator as shown at  624 , and secondary ear cup  202   b  can transmit CONDET pulses  626  to primary ear cup  202   a , as shown in plot  610 . After receiving the CONDET pulses from secondary ear cup  202   b , primary ear cup  202   a  can send CONDET confirmation pulses  628  to secondary ear cup  202   b , as shown in plot  208 . In some embodiments, the exchange of CONDET pulses  626 ,  628  signals that the connection has been established, and primary ear cup  202   a  and secondary ear cup  202   b  can enter normal operating mode (as indicated at  630 ) and begin using the data lines to communicate data, including audio to be played. 
     In some embodiments, the initialization events shown in  FIG.  6    can occur over a short period of time, so that the user experiences little or no perceptible delay between powering up the headphone system and the system being ready to use (at  630 ). Accordingly, the duration of the period during which headband ID pulses  620  are generated can be kept within a maximum limit consistent with an overall upper limit on the initialization time. For example, the duration of generating headband ID pulses  620  can be kept to 100 ms or less. (This duration parameter, in combination with the oscillator frequency of ASIC  412 , can set an upper limit on the number of pulses that can be included in headband ID pulses  620 ). 
     Headband ID circuit  410  provides a low-complexity (and low-circuit-area) implementation of headband identification. Other implementations are also possible. By way of example,  FIG.  7    shows a simplified schematic diagram of another headband ID circuit  710  coupled to a differential pair of data lines  722   a ,  722   b  according to some embodiments. Headband ID circuit  710  generates differential pulses on both of data lines  722   a ,  722   b . Like headband ID circuit  410 , headband ID circuit  710  can be an implementation of HBID circuit  210  of  FIG.  2   . Data lines  722   a ,  722   b  can be coupled between data contacts  332   a ,  334   a  in primary ear cup  202   a  and data contacts  332   b  and  334   b  in secondary ear cup  202   b . For instance, data lines  722   a ,  722   b  can be a subset (or all of) data lines  224  running the length of headband  204  and coupled to connectors  206  as shown in  FIG.  2   . 
     Headband ID circuit  710  includes ASIC  712 . ASIC  712  can include, e.g., an oscillator  732  that oscillates at a frequency in the kilohertz or megahertz range (e.g., ˜2 MHz). Oscillator  732  can be coupled to digital logic  734  that can generate output pulses on output paths  713   a ,  713   b . For example, digital logic  734  can be programmed to generate a specific (invariant, or fixed) number N of pulses, where N is the predetermined identification parameter value for a particular type of headband. In some embodiments, ASIC  712  can also include timer logic that imposes a fixed delay between when ASIC  712  is powered on and when ASIC  712  begins generating pulses on output paths  713   a ,  713   b.    
     Output path  713   a  provides a voltage at a base terminal of a transistor  714   a  that has a collector terminal coupled to data line  722   a  and emitter terminal coupled to ground. Similarly, output path  713   b  provides a voltage at a base terminal of a transistor  714   b  that has a collector terminal coupled to data line  722   b  and emitter terminal coupled to ground. In some embodiments, transistors  714   a ,  714   b  can be NPN-type bipolar junction transistors, which have reduced sensitivity to electrostatic discharge events as compared to a MOSFET; however, other types of transistors (including, e.g., NMOS or other MOSFETs) can be substituted. 
     ASIC  712  can draw operating power (VDD) from a capacitor  716  that is coupled to data lines  722   a ,  722   b  via resistors  718  and Schottky diodes  720 , which can help to prevent capacitor  716  from back-powering data lines  722   a ,  722   b  during normal operation (e.g., after headband identification is completed). A monitoring circuit  724  can be provided to control when ASIC  712  begins to generate time-varying outputs. For example, a comparator  726  can monitor the DC voltage on its input lines. DC voltage can increase as capacitor  716  charges. When the DC voltage reaches a threshold, controller  726  can trigger ASIC  712  to begin generating pulses. In some embodiments, ASIC  712  can trigger hysteresis in monitoring circuit  724  so that ASIC  712  can be turned off when DC voltage decreases again. 
     In operation, when both ends of data lines  722   a ,  722   b  become connected to ear cups, primary ear cup  202   a  can drive data lines  722   a ,  722   b  to a high-Z state, and capacitor  716  can begin to charge. Once capacitor  716  has charged to a sufficient level, monitoring circuit  724  can trigger ASIC  712  to begin generating pulses on output paths  713   a ,  713   b . (If desired, a timer can impose a delay, similarly to ASIC  412  described above.) Corresponding pulses are created on data lines  722   a ,  722   b . This creates a differential pulsed signal that can be sensed by secondary ear cup  202   b , which can detect and count the pulses, thereby determining the identification parameter. Operation can be similar or identical to operations and timing described above with reference to  FIGS.  5  and  6   . 
     In some embodiments, HBID circuit  712  can rely on a voltage boost provided by the secondary ear cup.  FIG.  8    shows a simplified schematic diagram of circuitry in a secondary ear cup  802   b  according to some embodiments. Secondary ear cup  802   b  can be similar to secondary ear cup  202   b  described above, with the same USB receiver circuitry as shown in  FIG.  3   , including USB receiver switch  340   b  inductively coupled to data contacts  332   b ,  334   b  in connector  330   b . In this embodiment, secondary ear cup  802   b  also includes a voltage boost circuit  804 , which can drive a higher than normal voltage on the data lines. Voltage boost circuit  804  can be switched on during headband identification and off thereafter using a switch  806  controlled by a timing signal  808 . Timing signal  808  can be generated at a fixed time after detecting the presence of a primary ear cup coupled to data contacts  332   b ,  334   b.    
     It will be appreciated that the headband ID circuits described herein are illustrative and that variations and modifications are possible. Any circuit components and associated values (e.g., resistances, capacitances, timing, etc.) identified in the drawings can be modified or different components can be substituted. In the examples shown, transistors are used to implement switches to create transient voltage drops on one or more data lines; other types of electronic switches can be substituted. Further, while the ASICs in the examples above generate pulses on the data line(s) that can be counted using circuitry in one of the ear cups, an ASIC can be configured to support a different encoding scheme, including encoding schemes that incorporate timing elements (e.g., time between pulses and/or duration of pulses) in addition to or instead of counting pulses. A variety of circuits can be used to communicate a stored or encoded headband-identification parameter value to an ear cup, provided that these circuits do not interfere with data communication between the ear cups after the headband-identification parameter value has been communicated. In some embodiments, such as the examples described herein, the headband ID circuit can be configured to enter and remain in a low-power state after sending the identification data. 
     As noted above, the connectors  206  at the two ends of headband  204  (or connector assemblies  106  at the two ends of headband  104 ) can be identically constructed, so that either end of headband  204  can be connected to either ear cup  202   a ,  202   b .  FIGS.  9 A and  9 B  illustrate reversibility of headband  204  according to some embodiments.  FIG.  9 A  shows headband  204  in a first orientation, with headband ID circuit  410  (of  FIG.  4   ) coupled to pull down on data line  922 , which in this orientation connects transmit contact  332   a  in primary ear cup  202   a  to receive contact  332   b  in secondary ear cup  202   b .  FIG.  9 B  shows headband  204  in a second orientation reversed from the orientation of  FIG.  9 A . Headband ID circuit  210  is coupled to pull down on the same data line  922 , which in this orientation connects transmit contact  334   a  in primary ear cup  202   a  to receive contact  334   b  in secondary ear cup  202   b . In these two orientations, headband ID circuit  210  pulls down on opposite-polarity data lines (D+ in one case, D− in the other), but in either case, a voltage differential is created that can be detected by the receiver in secondary ear cup  202   b . It should be understood that reversibility of a headband is not required. For instance, a headband can have disparate connectors at each end, and primary and secondary ear cups can have corresponding connectors such that one end of a headband is only connectable to a primary ear cup while the other end is only connectable to a secondary ear cup. 
     In some embodiments, a headband ID circuit such as HBID circuit  410  of  FIG.  4    or HBID circuit  710  of  FIG.  7    can be designed to occupy a small area so that it does not require a significant increase in size of the headband. For example, a headband ID circuit can be integrated into connector assembly  106  of  FIG.  1   . 
       FIGS.  10 A and  10 B  show bottom and top views of a printed circuit board (PCB)  1000  that incorporates a headband ID circuit according to some embodiments. PCB  1000  includes a tongue section  1006  and a tail section  1010 . Tongue section  1006  can include contact pads  1008 , which can be connected to external contacts  108  shown in  FIG.  1   . Tail section  1010  can include other circuitry, such as ASIC  1012  (which can be, e.g., ASIC  412  or ASIC  712  described above) and supporting circuit components (capacitors, resistors, diodes, transistors, etc.) for a headband ID circuit (e.g., any of the examples described above). The particular layout of tail section  1010  can be modified as desired. In some embodiments, an elongated and narrow profile can allow connector assembly  106  to be similarly elongated and narrow, which may be desirable for the esthetics and/or comfort of a headband. 
       FIGS.  11 A and  11 B  show a connector assembly  1100  according to some embodiments, with  FIG.  11 A  showing an assembled view and  FIG.  11 B  showing an exploded view. Connector assembly  1100  can be an implementation of connector assembly  106  of  FIG.  1    and can incorporate PCB  1000  of  FIGS.  10 A and  10 B . Connector assembly  1100  can include an end cap  1102  having openings therein exposing contacts  1108 , which can be electrically coupled via an insert-molded assembly  1116  to contact pads  1008  on PCB  1000 . Overmold  1104  and ground spring  1114  can secure PCB  1000  in place with tongue section  1006  inside end cap  1102  such that contacts  1108  are exposed. A ground ring  1118  can be provided around end cap  1102 . 
     PCB  1000  and connector assembly  1100  are illustrative, and variations and modification are possible. A particular size of a connector assembly or arrangement of components and contacts is not required. 
     Using circuits and techniques of the kind described above, a parameter value representing headband-identification information can be communicated from a headband ID circuit in a headband to an ear cup connected to the headband. The communication can occur automatically when the headband becomes attached to the ear cups. For example, as described above, secondary ear cup  202   b  can receive the identification pulse sequence and deliver a corresponding signal to MCU  344 . In some embodiments, MCU  344  (shown in  FIG.  3 B ) can be configured (e.g., programmed) to recognize the identification pulse sequence. For instance, in the example of  FIGS.  5  and  6   , MCU  344  can recognize the identification pulse sequence based on timing relative to other events in an initialization sequence. MCU  344  can also be configured to decode the pulse sequence (e.g., by counting pulses) to extract (or read) the identification parameter value. In some embodiments, an ear cup can use the identification parameter value locally, e.g., within MCU  344 . In some embodiments, the ear cup that receives the identification parameter value can communicate the identification parameter value to the other ear cup using the appropriate data path. Additionally or instead, an ear cup can communicate the identification parameter value to a host device with which the headphone system is communicably coupled. 
     An ear cup or host device that reads or receives a headband identification parameter value can use the parameter value in a variety of applications. For example, a host device can have a graphical user interface that renders an image of a connected headphone system, e.g., when reporting status of a headphone system or when assisting a user in identifying a headphone system to connect. In some embodiments, the host device can use the headband identification parameter value to modify the rendered image. For instance, if the parameter value maps to a headband color, the headband color can be modified according to the parameter value. Other aspects of appearance of a headband (e.g., width of the headband, presence/absence or type of padding) can also be modified to the extent that the identification parameter value can be mapped to various aspects of appearance. In some embodiments, the host device (or an ear cup) can use the headband identification parameter value to adjust an acoustic setting. For example, different types of headbands can exert different clamping forces on the ear cups, and the clamping force may alter the acoustic response profile of the ear cups. Accordingly, if the identification parameter value is mapped to an amount of clamping force or to a particular effect on acoustic response, the host device (or an ear cup) can modify an audio signal to compensate for the effect. In some embodiments, the ear cup (or a host device) can use the identification parameter value to adjust an on-head detection system. For example, some ear cups can include optical (e.g., infrared) sensor systems to determine when the ear cup has been positioned proximate to a user&#39;s ear. The behavior of the optical sensor system can depend on the toe-in angle of the ear cup, which can be different for different headband types. Accordingly, in some embodiments, the ear cup can adjust an angle of an optical sensor to compensate for differences in toe-in angle between headband types. In some embodiments, different headband types can have different effects on battery life. For instance, battery life can be affected by the length or construction of the power and data lines in the headband. Accordingly, in some embodiments, an ear cup or host device can use the headband identification parameter value to refine an estimate of remaining battery life. In some embodiments, some headband types may include active circuitry implementing “advanced” features (e.g., microphones to sample the acoustic environment or other sensors that can be used to monitor the environment or the user), and the headband identification parameter can indicate which (if any) advanced features are implemented. Accordingly, in some embodiments, an ear cup or host device can modify its behavior based on the availability or unavailability of various advanced features. A headband identification parameter as described herein can be used for any combination of any of these and/or other purposes. 
     While the invention has been described with respect to specific embodiments, one skilled in the art will recognize that numerous modifications are possible. For example, although the description makes reference to headbands that are designed to fit over the top of the user&#39;s head, other types of headbands exist, such as headbands that wrap around the back of the head or the like. Headband identification can be used with any type of headband. 
     The amount, content, and format of identification data or identification information can be varied as desired. The number of distinct identification parameter values can be defined based on the number of headband types to be distinguished. In some embodiments, up to 32 or up to 256 distinct parameter values can be supported; the particular upper limit is a matter of design choice and can be in the thousands or hundreds of thousands. Where headband types are distinguishable based on multiple attributes, lookup tables or the like can be used to map an arbitrary numerical parameter value to a particular combination of attributes. 
     As described above, identification data can be used to modify device behavior, including the production of sound by the ear cups, user interface features, and so on. Other behavior modifications and/or user-supportive operations can be implemented based on the identification data. 
     Various features described herein, e.g., methods, apparatus, computer-readable media and the like, can be realized using any combination of dedicated components and/or programmable processors and/or other programmable devices. The various processes described herein can be implemented on the same processor or different processors in any combination. Where components are described as being configured to perform certain operations, such configuration can be accomplished, e.g., by designing electronic circuits to perform the operation, by programming programmable electronic circuits (such as microprocessors) to perform the operation, or any combination thereof. Further, while the embodiments described above may make reference to specific hardware and software components, those skilled in the art will appreciate that different combinations of hardware and/or software components may also be used and that particular operations described as being implemented in hardware might also be implemented in software or vice versa. 
     Computer programs incorporating various features described herein may be encoded and stored on various computer readable storage media; suitable media include magnetic disk or tape, optical storage media such as compact disk (CD) or DVD (digital versatile disk), flash memory, and other non-transitory media. Computer readable storage media encoded with the program code may be packaged with a compatible electronic device. Additionally or instead, the program code may be provided separately from electronic devices (e.g., via Internet download or as a separately packaged computer-readable storage medium). 
     In some embodiments, the identification data can uniquely identify a particular cushioning member that belongs to a particular user; where this is the case, the identification data might be regarded as personally identifiable information. It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. For instance, in some embodiments, identification data for a cushion or tip need not be provided to any entity other than the earpiece or (optionally) a user-owned host device with which the earpiece interoperates. Users may be informed of and prompted to opt in to any sharing of data that may occur. 
     Thus, although the invention has been described with respect to specific embodiments, it will be appreciated that the invention is intended to cover all modifications and equivalents within the scope of the following claims.