Abstract:
A method and system of an embodiment of the present invention may involve receiving an invite message at a network port of a device to initiate a communication session with the device; identifying an address associated with the invite message; when the address corresponds to a first address, performing a first session initiation process to establish first communications via an audio port of the device; and when the address corresponds to a second address, performing a second session initiation process to establish second communications via the audio port of the device; wherein the second session initiation process differs from the first session initiation process. In addition, access to the audio port may involve determining a priority of the invite message; rejecting the invite message when the priority of the invite message is inferior relative to a priority of a current dialog; and accepting the invite message when the priority of the invite request is superior to the priority of the current dialog.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application claims priority to U.S. Provisional Patent Application No. 60/719,465, filed Sep. 22, 2005, which is hereby incorporated by reference herein in its entirety. 
     
    
     BACKGROUND INFORMATION 
       [0002]    Session Initiation Protocol (SIP) is a call control signaling protocol for Internet Protocol (IP) networks. SIP is designed to be device-agnostic—that is, it is intended to provide a highly flexible call signaling capability that is not tailored to the capabilities of any particular device. Analog telephone signaling, on the other hand, is device-specific and highly constrained because of the historical legacy of the services delivered to the device. As a result, many call features available in traditional analog telephone devices are not easily integrated in a SIP-based network. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]    In order to facilitate a fuller understanding of the exemplary embodiments of the present inventions, reference is now made to the appended drawings. These drawings should not be construed as limiting, but are intended to be exemplary only. 
           [0004]      FIG. 1  is an exemplary SIP-based network system, according to an embodiment of the present invention. 
           [0005]      FIG. 2  illustrates an exemplary implementation where a SIP Device is embedded in a FTTP network, according to an embodiment of the present invention. 
           [0006]      FIG. 3  illustrates an exemplary implementation where a SIP Device is embedded in an ATA device connected to an IP network, according to an embodiment of the present invention. 
           [0007]      FIG. 4  is an exemplary flowchart illustrating a method for determining access to an audio port based on contact addresses, according to an embodiment of the present invention. 
           [0008]      FIG. 5  is an exemplary flowchart illustrating a test and/or verification process, according to an embodiment of the present invention. 
           [0009]      FIG. 6  is an exemplary flowchart illustrating a telemetry process, according to an embodiment of the present invention. 
           [0010]      FIG. 7  is an exemplary flowchart illustrating a determination of relative priorities between dialogs, according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0011]    A system and process of an exemplary embodiment of the present invention provides the ability to recognize distinct contact addresses and invoke specific behavior based on the distinct contact addresses and further interact with normal voice calls. 
         [0012]      FIG. 1  is an exemplary SIP-based network system, according to an embodiment of the present invention. System  100  illustrates an exemplary system for supporting SIP communication, in particular providing access to a SIP device based on a contact address associated with an invite request. As illustrated, SIP Device  110  may be coupled to User Interface  114 . SIP Device  110  may include a SIP User Agent  112  for communicating across IP Network  120  to a SIP Server  122 . SIP Server  122  may provide communication to other SIP devices, as shown by SIP Element  130  and SIP element  132 , through IP Network  124 . The various components of system  100  may be further duplicated, combined and/or integrated to support various applications and platforms. Additional elements may also be implemented in the system to support various applications. A SIP-based network may also include an IP network, packet switched based network or other type of network. The elements referred to in the Figures may include other network or packet switched based elements. For example, the elements referred to as “SIP” may include other network devices, elements, components, etc. 
         [0013]    SIP Device  110  may represent a device that manages User Interface  114 . User Interface  114  may include a traditional telephone and other data communication device using voiceband or other signaling, including but not limited to data moderns, facsimile devices, teletype (TTY) equipment, etc. SIP Device  110  may contain SIP User Agent  112 . SIP User Agent  112  may be integrated with SIP Device  110  or remote from SIP Device  110 . SIP User Agent  112  may perform interworking between SIP signaling and user interface actions. For example, SIP User Agent  112  may manage an exchange of media (e.g., audio, etc.) between User Interface  114  and a Real Time Protocol (RTP) media stream of a media session set up by the SIP signaling. SIP Device  110  may originate calls to and receive calls from other users. SIP Device  110  may communicate through IP Network  120  to SIP Server  122 . In addition, SIP Device  110  may include a Network Port N for communicating through IP Network  120  and an Audio Port P for communication with User Interface  114 . 
         [0014]    SIP Server  122  may represent a SIP proxy or application server that acts on behalf of SIP Device  110 . For example, SIP Server  122  may manage a SIP Address of Record (AOR) on behalf of SIP Device  110 . SIP Device  110  may register with SIP Server  122  and send SIP signaling through SIP Server  122  to other SIP elements, such as SIP Element  130  and SIP Element  132 . For example, a call to the SIP AOR may be delivered to SIP Server  122 , which in turn delivers the call to SIP Device  110 . SIP Server  122  may perform some service on behalf of SIP Device  110 , or may simply forward SIP messages to and from SIP Device  110 . SIP Device  110  communicates through IP Network  124  to SIP Element  130  and/or SIP Element  132 . 
         [0015]    SIP Element  130  and SIP Element  132  may represent users with which the user of SIP Device  110  communicates. SIP Element may be a SIP Device, SIP Server, and/or other SIP enabled device. In addition, SIP Element may also represent a PSTN device that may be reached by a gateway that, directly or indirectly, acts as a SIP User Agent. 
         [0016]    According to an embodiment of the present invention, SIP Device  110  may recognize various distinct contact addresses and provide corresponding distinct modes of access to Audio Port P. Access may include normal voice calling, verification access, test access, telemetry access and/or other access. In addition, priority rules may be implemented to grant access based on relative priorities determinations when a request is received during an established dialog. 
         [0017]      FIGS. 2 and 3  show exemplary implementations of a SIP Device.  FIG. 2  illustrates an exemplary implementation where a SIP Device is used in connection with a Fiber-to-the-Premises (MP) network, according to an embodiment of the present invention.  FIG. 3  illustrates an exemplary implementation where a SIP Device is embedded in an Analog Telephone Adapter (ATA) which is used in connection with a traditional (e.g., electrical) IP-enabled access network, according to an embodiment of the present invention. Other implementations with other devices and/or networks may also be realized. 
         [0018]    As shown in  FIG. 2 , User Interface  114  may be connected to SIP Device  110 . SIP Device  110  may be embedded in Optical Network Terminal (ONT)  210  or otherwise integrated. ONT  210  may be connected to an Optical Line Terminal (OLT)  230  via a Passive Optical Network (PON)  220  acting as an access network for communications between ONTs  210  and OLTs  230 . According to an exemplary application, OLT  230  may be located at a Central Office. ONT  210  may be connected over PON  220  to the OLT  230 , which in turn passes that connection through transport IP network  120  to SIP Server  122 . According to an exemplary application, OLT  230  may maintain an IP connection between SIP Device  110  on the ONT  210  and the transport IP network  120 . In this exemplary application, the OLT  230  may not process SIP signaling, but rather allows SIP signaling to pass through to its destination. 
         [0019]      FIG. 3  illustrates SIP Device  110  embedded in an Analog Telephone Adapter (ATA)  310  in a home or other location that subscribes to a broadband service delivered via an access network, such as DSL or cable modem service. The ATA device may be attached to a network, such as a broadband data network, IP network and/or other network. User Interface  114  may be connected to SIP Device  110 . ATA  310  may be connected to Broadband Router  320 , which in turn may be connected to a DSL or cable modern  330 , which in turn may be connected to access network  340 . Access network  340  may provide connectivity to transport IP network  120  through which the SIP Device  110  may communicate with SIP Server  122 . In one example, as shown in  FIG. 3 , data multiplexer (MUX)  350  may provide a point of connection for transmissions between access network  340  and the transport IP network  120 . 
         [0020]    The various components of systems  200  and  300  as shown in  FIGS. 2 and 3  may be further duplicated, combined and/or integrated to support various applications and platforms. Additional elements may also be implemented in the systems described above to support various applications. 
         [0021]    In an Internet Protocol (IP) network using the Session Initiation Protocol (SIP) for voice call control signaling, it may be desired to provide the equivalent of test, verification, and telemetry access to an analog telephone line (or equivalent) managed by a SIP User Agent. Such access may involve exchange of audio signals with the line, without normal call control signaling (e.g., power ringing, loop closure, etc.). An embodiment of the present invention provides a method and system for using SIP signaling to provide such access. Instead of relying upon protocols other than SIP, or on non-standard SIP extensions, an embodiment of the present invention may involve a SIP User Agent recognizing distinct contact addresses as having certain properties that invoke behavior appropriate for test, verification, telemetry and/or other access to an analog line. Further, an embodiment of the present invention minimizes and/or eliminates undesirable interactions with normal voice calls. 
         [0022]    In the public switched telephone network (PSTN), an analog line that is normally used for originating and receiving voiceband telephone calls may at times also be accessed from the network for alternate purposes other than handling calls. Such alternative purposes may include test access, telemetry, busy line verification and/or other purposes. Test access may involve providing a connection from a test trunk to a subscriber line, for various manual and/or automatic testing purposes. Telemetry access may involve providing a connection to a telemetry device that shares a subscriber line (e.g., remote meter reading, etc.). Busy line verification access may involve providing a connection from a verification operator to a subscriber line for the purpose of determining whether there is conversation on a busy line or other activity. In addition, busy verification access may provide the ability for the operator to break into a call. These functions may be provided by a central office switch to loop-start analog lines. 
         [0023]    The PSTN is evolving from its legacy technology base of analog and time-division multiplex (TDM) transport and signaling to a technology base using Internet Protocol (IP) transport and signaling protocols. However, the IP-based network will continue to support legacy analog subscriber equipment (e.g., analog phones, faxes, moderns). A mechanism for supporting analog equipment in the IP network may include a line media gateway deployed at the “edge” of the network, which uses IP signaling protocols that may be designed specifically for the gateway application. Gateway signaling protocols may operate at a relatively low level, and may thus easily support the functions of test access, busy line verification, telemetry and/or other alternate purposes with respect to analog subscriber equipment. 
         [0024]    As IP signaling reaches more edge devices, SIP may be implemented as a call control signaling protocol for analog subscriber devices. For example, SIP signaling may meet analog subscriber equipment at devices such as Integrated Access Devices, Analog Telephone Adapters, and Optical Network Terminals. Such devices may manage one or more connections to analog devices, and may contain SIP User Agents that perform the translation between the analog line signaling expected by such analog devices and SIP protocol messages. In addition, SIP may also replace gateway control protocols in line media gateways. In contrast with gateway control protocols, which may be described as device control protocols, SIP may be considered a relatively high-level call control protocol. 
         [0025]    As SIP is generally independent of the particular device used to originate and receive a call, SIP is typically not designed to provide direct access to an audio port of an edge device (e.g., the analog line) for purposes such as testing, busy line verification, or telemetry. An embodiment of the present invention provides audio port access for alternate purposes using standard SIP signaling. 
         [0026]    An embodiment of the present invention may involve a device with a port to an analog user interface and a port to a network. The device may include SIP Device  110  which may include SIP User Agent  112 , as shown in  FIG. 1 . A first port, as shown by Audio Port P, may be connected to one or more analog user interfaces, such as User Interface  114 . For example, User Interface  114  may include telephones or other communication devices, through which a user originates and receives calls as well as perform other form of communication. In addition, Audio Port P may also connect to one or more devices that may not be typically used to originate or receive calls, but may communicate using voiceband and/or other signaling to perform various functions, such as test, verification, telemetry, etc. A second port, as shown by Network Port N, may be connected to network  120 , which may include intermediate nodes (e.g., routers, switches, etc.). Network Port N may permit communication with a remote SIP element over network  120 . The remote SIP element may in fact be a point of connection to a network composed of many elements. For example, the remote SIP element may include a SIP Server  122 , a proxy server, an application server, a User Agent and/or other devices, including a SIP enabled device and/or other network enabled device. The remote SIP element may originate calls to and receive calls from SIP Device  110  using SIP signaling, such as described below. Using the method described in accordance with the various embodiments of the present inventions and embodied in SIP User Agent  112  in SIP Device  110 , the remote SIP element may also obtain access to Audio Port P for various purposes including testing, busy line verification, telemetry and/or other purposes. 
         [0027]    SIP Device  110  may contain more than one Audio Port P, each such port capable of supporting at least one associated User Interface  114 . While the description and Figures illustrate a single audio port, additional audio ports, devices and/or components may be implemented. In addition, an Audio Port P may communicate with additional devices, such as multiple user agents, if such a configuration is desired. Further, the various elements may be further integrated, combined and/or separated across multiple components. Other architectures and scenarios may be implemented. 
         [0028]    According to an exemplary scenario associated with a typical voice communication session, a remote SIP element may originate a call or other communication session to SIP Device  110 . The process may begin with a SIP INVITE message sent from the remote SIP element to SIP User Agent  112  in SIP Device  110 . The SIP INVITE message may be received by SIP Server  122  with which the SIP Device  110  has registered. The SIP Server  122  may perform address mapping and/or some admission control actions and forward the SIP INVITE to SIP Device  110 . Upon receiving the INVITE message, SIP User Agent  112  may alert the user by some form of signaling transmitted through Audio Port P to one or more user interfaces connected to Audio Port P, which may include an attached communication device. When alerting begins, SIP User Agent  112  may send a “180 Ringing” message to the remote SIP element. The user may respond by performing an action such as picking up a handset or other acknowledgement. The action may then cause the user interface to transmit a signal through Audio Port P to SIP User Agent  112 . In response, SIP User Agent  112  may send a “200 OK” message to the remote SIP element. The remote SIP element may then send an acknowledgement, e.g., ACK message, to SIP User Agent  112 . During the INVITE/200 OK/ACK exchange with SIP User Agent  112 , the remote SIP element may agree on audio session parameters. Upon reaching an agreement, the remote SIP element may exchange audio (or other data) between the device(s) attached to Audio Port P and an equivalent device at the remote SIP element. SIP User Agent  112  may track the state of the resulting call session. Eventually, one party may end the call by taking an action that results in a BYE message being sent. The element receiving the BYE message may respond with a “200 OK” message. A call originated by SIP Device  110  may begin with the user performing an initiation action, such as picking up a handset and dialing a number, whereupon SIP User Agent  112  in SIP Device  110  sends an INVITE message to SIP element. The call proceeds as described above, with SIP element and SIP Device  110  swapping roles. 
         [0029]    The SIP User Agent  112  may manage more than one dialog simultaneously on behalf of Audio Port P. If multiple dialogs exist, some may be “on hold” and others may be “active.” If more than one dialog is active, the audio for the dialogs may be mixed, thereby forming a conference. Audio Port P may support a single audio stream or multiple audio streams which may be switched from one dialog or a set of dialogs to another dialog or another set of dialogs. Accordingly, in SIP Device  110 , Audio Port P may have no dialogs, one dialog or more multiple voice dialogs at any given time. 
         [0030]    As noted above, a SIP dialog initiated by a SIP INVITE may correspond to a call and/or other form of communication between and/or among SIP devices and/or other communication devices. In the preferred embodiments described herein, a SIP dialog may not only include a typical voice dialog, but also a test dialog, a verification dialog, a telemetry dialog and/or other one-way or multiple-way communication of data specific to user interface equipment. In the preferred embodiment, SIP User Agent  112  may register a contact address with a “registrar” function in a SIP element (e.g., SIP Server  122 ). The contact address represents a unique address to which normal calls may be delivered. SIP User Agent  112  may also register alternate contact addresses associated with functionality supported by SIP Device  110  for interfacing with Audio Port P. For example, SIP User Agent  112  may register with its associated SIP Server  122  an address “A” which it may use for voice calling, an address “T” which it may use for telemetry sessions, and an address “V” which it may use for test/verification sessions. SIP User Agent  112  will interpret SIP INVITE messages directed to these addresses as requests for the special sessions that require alternate treatment, as further described below. Other addresses may also be used to represent other access, purpose or function, if such are provided by SIP Device  110 . 
         [0031]    According to an exemplary application, test, verification, and telemetry access may be initiated by a remote SIP element and directed to the appropriate alternate SIP address associated with the SIP Device  110 . Upon receipt of the SIP INVITE directed to the alternate SIP address, SIP User Agent  112  may initiate an alternative session establishment process which accommodates the unique functionality of the requested service. For example, a test, telemetry or verification dialog may utilize means other than the usual and customary means for alerting and/or answering at analog devices connected to the Audio Port P of the SIP Device  110 . For example, the dialog may be established without providing a “ringing” signal to the user interface device—which may allow a telemetry device (or other device) attached to the Audio Port P to “answer” and communicate data. In addition, a test, telemetry or verification dialog may have a priority relationship with respect to other dialogs, such that it may be rejected in favor of other dialogs, and may also preempt or be preempted by other dialogs. Further, a test, telemetry or verification dialog may join with another dialog that is active, or may become active, at the audio port of the device. Other types of dialog may be established in accordance with the various embodiments of the present invention. 
         [0032]    The preferred embodiments described herein may thus provide access to the audio ports of a SIP Device  110  via a SIP-established session, which may occur without disrupting the normal calling activities of the user and may accommodate the specific requirements of analog subscriber equipment. 
         [0033]      FIG. 4  is an exemplary flowchart illustrating a method for determining access to an audio port based on contact addresses, according to an embodiment of the present invention. At step  410 , an INVITE request may be received at a device, such as a SIP User Agent  112  in SIP Device  110 . The INVITE request may be specific to a particular contact address. The contact address may include an address or any other identifier. At step  412 , a corresponding service supported by the SIP Device  110  may be identified for the contact address in the received INVITE request. For example, an INVITE to address “A” may be recognized as a request for a voice dialog at step  414 . As a result, a voice dialog may be established as shown by step  416 , in a manner that is well known. An INVITE to address “V” may be recognized as request for a verification dialog at step  418  and a verification dialog may be established as shown by step  420  (further described below). An INVITE to address “T” may be recognized as a request for a telemetry dialog at step  422  and a telemetry dialog may be established at step  424  (further described below). In addition, an embodiment of the present invention may receive INVITE messages to other addresses which may correspond to other services available on SIP Device  110  that have special processing requirements and/or provide other access. Step  426  represents an end of the process. 
         [0034]    According to an embodiment of the present invention, priority rules may be implemented. The priority rules may apply when a request to establish a new dialog is received while a dialog is currently established. The existing dialog may be active, on hold or other status. For example, test and verification access to Audio Port P may involve connecting to an audio stream at Audio Port P regardless of the number of voice dialogs associated with Audio Port P. If no voice dialog is currently associated with Audio Port P, the test/verification audio stream may be a bidirectional exchange of audio with Audio Port P. If a voice dialog exists, then the test/verification audio stream may be mixed with the audio stream that exists between Audio Port P and a far end of the dialog. According to another example, telemetry access may involve a bidirectional exchange of audio with Audio Port P, making telemetry access to Audio Port P mutually exclusive with voice dialogs. Priority rules may arbitrate establishment of voice and telemetry dialogs in such cases. Other priority rules and/or conditions may also be applied. 
         [0035]      FIG. 5  is an exemplary flowchart illustrating a test and/or verification process, according to an embodiment of the present invention. At step  510 , an INVITE to address V may be received. The INVITE to address V may be transmitted from a remote SIP element and received by a SIP User Agent in a SIP device which, for example, has registered address V as an address at which test/verification sessions with the Audio Port P associated with the SIP user Agent may be directed. It may be determined whether the INVITE to address V is properly authenticated, at step  512 . If it is not properly authenticated, the INVITE to address V may be rejected, at step  514 . At step  516 , it may be determined whether a verification dialog already exists associated with Audio Port P. If so, the INVITE may be rejected. In addition, other determinations may be made and the INVITE may be rejected for other reasons. 
         [0036]    If a verification dialog does not already exist, the INVITE to address V may be accepted at step  520 . In addition, the INVITE to address V may be accepted at step  520  regardless of the existence of any voice dialogs. Once the INVITE to address V is accepted, a signaling process associated with test/verification processing may be executed in the course of establishing a test/verification session. For example, standard “ringing” signaling may not be provided on Audio Port P, but rather a media session for a verification dialog may be established, as shown by step  522 , thus allowing for test/verification signals to be applied at Audio Port P. If a voice dialog does not exist, as determined at step  524 , or any existing voice dialogs are on hold, as determined by step  528 , the media session established for the verification dialog may exchange bidirectional audio with Audio Port P, at step  526 . If one or more voice dialogs are active, as determined by step  530 , audio streams may be mixed, as shown by step  532 , such that the verification dialog receives audio from Audio Port P and active voice dialogs, and transmits audio to Audio Port P and active voice dialogs. 
         [0037]      FIG. 6  is an exemplary flowchart illustrating a telemetry process, according to an embodiment of the present invention. At step  610 , an INVITE to address T may be received. The INVITE to address T may be transmitted from a remote SIP element and received by a SIP User Agent in a SIP device which, for example, has registered address T as an address at which telemetry sessions with Audio Port P associated with the SIP User Agent may be directed. It may be determined whether the INVITE to address T is properly authenticated, at step  612 . If not properly authenticated, the INVITE to address T may be rejected, at step  614 . At step  616 , it may be determined whether a telemetry or verification dialog already exists. If so, the INVITE to address T may be rejected, at step  618 . In addition, other determinations may be made and the INVITE may be rejected for other reasons. It may be determined whether a voice dialog exists, at step  620 . If not, the INVITE to address T may be accepted at step  622 . If a voice dialog exists, a determination of priorities between the current request and any existing dialogs may be initiated, at step  624 . Based on the priorities, the INVITE may be rejected at step  626  or accepted at step  628 . If the INVITE to address T is accepted, a signaling process associated with telemetry processing may be executed in the course of establishing a telemetry session. For example, standard “ringing” signaling may not be provided on Audio Port P, but rather specialized electrical signaling may applied at Audio Port P as may be expected by a telemetry device. If a telemetry dialog is established (e.g., the telemetry device responds), an associated media session may exchange bidirectional audio with Audio Port P. 
         [0038]      FIG. 7  is an exemplary flowchart illustrating a determination of relative priorities between dialogs, according to an embodiment of the present invention. The relative priorities of telemetry and voice dialogs may determine which dialog takes precedence. The priority of a dialog may be specified by a “Priority” field in the header of the INVITE message that establishes the dialog. If a “Priority” field is not present, the priority may default to “normal” or other predetermined default.  FIG. 7  illustrates an exemplary determination of priorities between or among dialogs. Other relative priorities may be established. 
         [0039]    For example, when an INVITE, to address T is received while one or more voice dialogs exist, a determination of priorities may be made. At step  710 , if the priority associated with the INVITE to address T is less than or equal to that of at least one existing voice dialog, the INVITE to address T may be rejected, as shown in step  712 . According to an exemplary application, an INVITE to address T may have a lower priority than a voice dialog. However, if the INVITE to address T has a higher priority than existing voice dialogs, the INVITE to address T may be accepted at step  714 . If the voice dialog is active, as determined by step  716 , the active voice dialog may be placed on hold at step  718  and a telemetry dialog may be established as shown by step  720 . At this point, the user may not activate a voice dialog until the telemetry dialog ends. According to another example, an INVITE to address A may be received at step  722  during a time period when a telemetry dialog exists. The corresponding priorities of the requested call session and the existing telemetry session may be similarly compared. If the priority of the INVITE to address A is greater than the priority of the telemetry dialog as shown by step  724 , the telemetry dialog may be terminated at step  728  and the voice dialog may be established at step  730 . Otherwise, the telemetry dialog may continue as shown by step  726 , and the INVITE to address A may be rejected. Other priorities may be implemented in accordance with the various embodiments of the present invention. 
         [0040]    While the processes of  FIGS. 4 ,  5 ,  6  and  7  illustrate certain steps performed in a particular order, it should be understood that the embodiments of the present invention may be practiced by adding one or more steps to the processes, omitting steps within the processes and/or altering the order in which one or more steps are performed. 
         [0041]    By recognizing the various distinct contact addresses, User Agent  112  in SIP Device  110  may provide corresponding distinct modes of access to Audio Port P, which may include normal voice calling, verification access, test access, telemetry access and/or other access. According to an embodiment of the present invention, User Agent  112  may provide these functions utilizing standard SIP signaling. As a result, SIP extensions are not required, non-standard protocols are not required, and protocols beyond those used for normal voice calling are not required. According to an exemplary application, standard SIP signaling may be used for providing verification, telemetry access and/or other access. 
         [0042]    In the preceding specification, various preferred embodiments have been described with reference to the accompanying drawings. It will, however, be evident that various modifications and changes may be made thereto, and additional embodiments may be implemented, without departing from the broader scope of the invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense.