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RELATED APPLICATION  
       [0001]    This application claims priority to U.S. Provisional Patent Application Serial Number 60/422,013, filed on Oct. 29, 2002, entitled REMOTELY OPERABLE VENT CAP, which is herein incorporated by reference. 
     
    
     
       TECHNICAL FIELD  
         [0002]    This invention relates generally to plumbing systems for domestic, commercial and industrial waste systems and particularly, but not by way of limitation, to systems and methods of remotely opening a vent in a plumbing system.  
         BACKGROUND  
         [0003]    At the time of installation, waste plumbing systems for residential and commercial building structures are tested for leaks. An uncorrected leak in a waste system can allow buildup of dangerous fumes within the structure. Testing involves filling drain traps with water and installing a cap on the plumbing vent. Typically, the vent is located on the roof of the building. With the system thus sealed, a regulated air pressure is applied to the waste system and various methods are used to identify any leaks. Following the testing procedure, the roof vent cap is removed.  
           [0004]    To remove the vent cap, a worker typically ascends the building with the aid of a ladder and physically removes the cap. The cap may be a threaded or unthreaded fitting which provides an air tight seal with the vent pipe.  
           [0005]    Removing the vent cap is not without hazards or inconvenience. For example, falls from atop the building roof have injured many plumbers. In addition, the ladder can be a dangerous tool near power lines. Furthermore, the plumber is forced to carry, or at least have available, a suitable ladder.  
           [0006]    What is needed is an improved system and method for removing a vent cap.  
         SUMMARY  
         [0007]    A remotely operable vent stop includes a wireless receiver coupled to a release mechanism. The wireless receiver, in one embodiment, includes an audio frequency transducer. The release mechanism, in one embodiment, includes an electrically disbonding adhesive joint between an upper and lower portion. A voltage applied across the joint will weaken and disbond the joint. A compressed spring applies a force between the two portions and ejects the upper portion, or housing from the lower portion, or coupler, when the adhesive is disbonded. The terms coupler and coupling are used interchangeably herein.  
           [0008]    In one embodiment, the housing includes a vent stop. When the vent stop is secured to the coupling, and the coupling is affixed to a plumbing vent, an airtight seal is formed on the vent.  
           [0009]    In an exemplary embodiment, the system includes a remote unit and a local unit. The remote unit is adapted for affixation to a vent pipe and includes a separable upper portion held in alignment with a plumbing system vent pipe by a bonded joint. The local unit is adapted for temporary coupling with an accessible pipe fitting, also coupled to the plumbing system, and for generating a predetermined audio signal within a bore or lumen of the plumbing system. The remote unit, upon receiving the predetermined audio signal, applies a voltage across the bonded joint and after a predetermined current has passed, an adhesive positioned within the joint disbonds. A spring urges the upper portion to separate from the vent pipe following disbonding of the joint. The upper portion falls from the vent pipe, thus opening the vent to the atmosphere. The upper portion may be recovered from the roof or ground.  
           [0010]    In one embodiment, the plumbing stop includes a plug having external threads which engages internal threads of the vent pipe. In one embodiment, the plumbing stop includes a cap having internal threads which engages external threads of the vent pipe.  
           [0011]    Other aspects of the invention will be apparent on reading the following detailed description of the invention and viewing the drawings that form a part thereof.  
           [0012]    This summary is intended to provide a brief overview of some of the embodiments of the present system, and is not intended in an exclusive or exhaustive sense, and the scope of the present subject matter is to be determined by the attached claims and their equivalents. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    In the drawings, like numerals describe substantially similar components throughout the several views. Like numerals having different letter suffixes represent different instances of substantially similar components.  
         [0014]    [0014]FIG. 1 illustrates a plumbing system for a residential building with one embodiment of the present subject matter.  
         [0015]    [0015]FIG. 2 includes a block diagram of one embodiment of the present subject matter.  
         [0016]    [0016]FIG. 3 includes a block diagram of a processor controlled embodiment of the present subject matter.  
         [0017]    [0017]FIG. 4 includes a cross sectional view of one embodiment of the present subject matter.  
         [0018]    [0018]FIG. 5 includes a cross sectional view of portions of one embodiment of the present subject matter having multiple ejection springs.  
         [0019]    [0019]FIGS. 6A and 6B illustrate cross sectional views of one embodiment having a sliding spring contact and a single ejection spring.  
         [0020]    [0020]FIG. 7 includes a flow chart of a method of manufacturing one embodiment of the present subject matter.  
         [0021]    [0021]FIGS. 8A and 8B illustrate cross sectional views of one embodiment of the present subject matter having a conical spring.  
         [0022]    [0022]FIGS. 9A, 9B,  9 C and  9 D illustrate views of a splined coupling embodiment.  
         [0023]    [0023]FIG. 10 includes an exploded view of a motor controlled embodiment.  
         [0024]    [0024]FIG. 11 illustrates a sectional view of a gravity assisted embodiment.  
         [0025]    [0025]FIG. 12 illustrates a detail view of a portion of one embodiment.  
         [0026]    [0026]FIG. 13 includes a cross sectional view of one embodiment of the present subject matter having an engagement spring held in position by an electrically releasable adhesive joint.  
         [0027]    [0027]FIG. 14 includes a piezoelectric transducer coupled to an upper housing.  
         [0028]    [0028]FIG. 15 includes an exploded view of a sounder and a plumbing fitting.  
         [0029]    [0029]FIG. 16 includes a flow chart of a method of using one embodiment of the present subject matter. 
     
    
     DETAILED DESCRIPTION  
       [0030]    In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that the embodiments may be combined, or that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents. In the drawings, like numerals describe substantially similar components throughout the several views. Like numerals having different letter suffixes represent different instances of substantially similar components.  
         [0031]    The present subject matter includes methods, apparatus and systems as described herein.  
         [0032]    [0032]FIG. 1 illustrates how one embodiment of the present subject matter may be used with a drain, waste and vent (DWV) piping system. The figure illustrates a cut-away view of a residential house with main sewer stack  160  and secondary sewer stack  165 . Stack  160  and stack  165  pass through the roof of the house and each terminates at their upper ends with vent  100 . In the figures, remote units  200  are affixed to each vent  100 . Following testing of the DWV plumbing system, the remote units are removed from the vents.  
         [0033]    A block diagram of remote unit  200 B is illustrated in FIG. 2. Communication module  205  is coupled to a release mechanism  210 . In one embodiment, communication module  205  includes an audio transducer adapted to receive a modulated audio signal propagated within a lumen of the plumbing system. For example, when a predetermined audio input signal is introduced at fitting  145 , the signal is propagated through stack  160  to vent  100  and received by remote unit  200 A. Upon receiving the audio signal, communication module  205  provides a release signal to release mechanism  210 . When release mechanism  210  is activated, a stop of remote unit  200 B is ejected from the vent, thus preparing the DWV piping system for service. The stop provides an air-tight seal with the DWV piping system and activation of the release mechanism allows the stop to be freely removable from the piping system. The stop includes a device that occludes the bore of a pipe. In various embodiments, the stop includes a plumbing cap, plug or valve.  
         [0034]    [0034]FIG. 3 illustrates an embodiment of remote unit  200 C with processor  330 . Supply  260  is coupled to processor  330 , communication module  205 B and release mechanism  210 B. In one embodiment, processor  330  receives an electrical signal from communication module  205 B, processes the signal through one or more logic gates and provides an electrical release signal to release mechanism  210 B provided the received signal meets predetermined parameters. In one embodiment, processor  330  includes analog circuitry for generating a release signal upon receiving a predetermined input signal. In one embodiment, processor  330  includes digital circuitry for generating a release signal upon receiving a predetermined input signal. In one embodiment, processor  330  includes a microprocessor.  
         [0035]    In one embodiment, the housing is affixed to the coupling, or the vent pipe, by an electrically disbanding adhesive. The adhesive is disposed in a thin layer between two electrically conductive surfaces. A voltage applied between the two conductive surfaces having sufficient electromotive force (EMF) and for a predetermined duration, causes the adhesive bond to weaken and eventually release. In one embodiment, the electrically releasable adhesive includes an epoxy resin such as ElectroRelease E4™, (EIC Laboratories of Norwood, Mass.).  
         [0036]    [0036]FIG. 4 illustrates a view of an embodiment of remote unit  200 D. Housing  250 A and coupling  320 A are fabricated of polyvinyl chloride (PVC) plastic. Housing  250 A, in one embodiment, includes a vent stop. Coupling  320 A is adapted to fit within plumbing vent pipe  100 . Vent  100  is coupled to a DWV plumbing system and provides venting to a fresh air supply. Coupling  320 A includes electrodes  280 A which are electrically coupled to a ground connection. In one embodiment, the ground connection is provided by an interconnecting wire buried within coupling  320 A which connects electrode  280 A with spring  275 A which is electrically connected to supply ground. In one embodiment, the ground connection is provided by a leaf spring contact between coupling  320 A and housing  250 A. Coupling  320 A receives a portion of housing  250 A. Piezoelectric transducer  315 A is coupled to housing  250 A and electrically coupled to processor  330 . Processor  330  is coupled to ground and is powered by supply  260 . Disbonder  335  is powered by supply  260  and provides a disbonding current to adhesive  290  when processor  330  triggers disbanding on control line  336 . In one embodiment, disbonder  335  can be modeled as a switch and a voltage multiplier, where the switch is operated by control line  336  and the output of disbonder  335  includes an increased supply voltage provided to adhesive  290 . In one embodiment, disbonder  335  includes an electrical switch, the state of which is controlled by control line  336 . Electrodes  280 A and electrodes  285 A are bonded together with electrically disbanding adhesive  290 .  
         [0037]    Springs  275 A are depicted in a compressed mode and each applies a force to urge separation of housing  250 A and coupling  320 A. Springs  275 A are coil springs. Seal  265 A is disposed between a surface of housing  250 A and coupling  320 A and in the embodiment shown, seal  265 A includes a rubber o-ring. In one embodiment, seal  265 A includes a gasket. In one embodiment, seal  265 A mates with an annular sealing surface. In one embodiment, seal  265 A includes a TEFLON™ product. TEFLON™ is a registered trademark of E. T. du Pont de Nemours and Company of Wilmington, Del. The ground connections of electrodes  280  are electrically bonded to the ground connection of housing  250 A. Seal  265 A, springs  275 A and electrodes  285 A are affixed to housing  250 A. After releasing, electrodes  280 A remain affixed to coupling  320 A and coupling  320 A remains affixed to vent  100 .  
         [0038]    At the time of installation of remote unit  200 D, springs  275 A are compressed between housing  250 A and coupling  320 A; electrodes  280 A are bonded to electrodes  285 ; and seal  265 A, and housing  250 A, provide an airtight seal on coupling  320 A. Coupling  320 A is coupled to vent  100  with an airtight joint.  
         [0039]    To remotely separate housing  250 A from coupling  320 A, a modulated audio signal, shown at  345 , is propagated through the lumen of vent  100 . Modulated audio signal  345  is received by transducer  315 A and an electrical signal is supplied to processor  330 . Processor  330 , having received an electrical signal from transducer  315 A corresponding to audio modulated with a predetermined signal, provides a control signal to disbonder  335 . When disbonder  335  is energized, a voltage is applied across adhesive  290 . Adhesive  290  is weakened upon exposure to an electric current and when sufficiently weak, the bond fails and energy stored in compressed springs  275 A overcomes the joint and housing  250 A is ejected from coupling  320 A. Upon ejection, seal  265 A no longer provides an air tight seal for vent  100 . Housing  250 A, along with seal  265 A, springs  275 A, electrodes  285 A, supply  260 , disbonder  335 , processor  330  and transducer  315 A are ejected from coupling  320 A. When installed on vent  100  and separated as herein described, coupling  320 A remains attached to vent  100  and housing  250 A is ejected and may fall on the roof of the building or tumble to the ground.  
         [0040]    [0040]FIG. 5 illustrates a cross sectional view of portions of an embodiment of remote unit  200 E where the electrically disbonding adhesive is subjected to a shear load. Housing  250 B and coupling  320 B are fabricated of PVC plastic. Coupling  320 B is adapted to fit around an external surface of plumbing vent pipe  100 . Coupling  320 B includes electrodes  280 A which are electrically coupled to a ground connection. In one embodiment, the ground connection is provided by an interconnecting wire buried within coupling  320 B which connects electrode  280 A with spring  275 A and spring  275 A is electrically connected to a supply ground. In one embodiment, the ground connection is provided by a leaf spring contact between coupling  320 B and housing  250 B.  
         [0041]    Housing  250 B receives a portion of coupling  320 B. Piezoelectric transducer  315 A is coupled to housing  250 B and electrically coupled to processor  330 . Processor  330 , supply  260 A, supply  260 B, switch  340  are disposed within a cavity of housing  250 B. Electrodes  280 A and electrodes  285 A are bonded together with electrically disbonding adhesive  290 . Springs  275 A are depicted in a compressed mode and each applies a force to urge separation of housing  250 B and coupling  320 B. Seal  265 A is disposed between a surface of housing  250 B and coupling  320 B and in the embodiment shown, seal  265 A includes a rubber o-ring. The ground connections of electrodes  280 A are electrically bonded to the ground connection of housing  250 B. Seal  265 A, springs  275 A and electrodes  285 A are affixed to housing  250 B.  
         [0042]    At the time of installation of remote unit  200 E, springs  275 A are compressed between housing  250 B and coupling  320 B; electrodes  280 A are bonded to electrodes  285 A; and seal  265 A, and housing  250 B, provide an airtight seal on coupling  320 B. Coupling  320 B is coupled to vent  100  with an airtight joint.  
         [0043]    To remotely separate housing  250 B from coupling  320 B, a modulated audio signal is propagated through the lumen of vent  325 . The modulated audio signal is received by transducer  315 A and an electrical signal is supplied to a processor. The processor, having received an electrical signal from transducer  315 A corresponding to audio modulated with a predetermined signal, provides a control signal to close a switch. When the switch is closed, a voltage is applied across adhesive  290 . Adhesive  290  is weakened upon exposure to an electric current and when sufficiently weak, the bond fails and energy stored in compressed springs  275 A overcomes the joint and housing  250 B is ejected from coupling  320 B. Upon ejection, seal  265 A no longer provides an air tight seal for vent  325 . Housing  250 B, along with seal  265 , springs  275 A, electrodes  285 A, as well as the circuitry coupled to adhesive  290  and piezoelectric transducer  315 A are ejected from coupling  320 B. When installed on vent  100  and separated as herein described, coupling  320 B remains attached to vent  100  and housing  250 B is ejected and may fall on the roof of the building or tumble to the ground.  
         [0044]    [0044]FIG. 6A illustrates a cross sectional view of an embodiment of the present subject matter where the electrically disbonding adhesive is subjected to a shear load. In the figure, remote unit  200 G includes housing  250 C and coupling  320 C, both of which are fabricated of PVC plastic. Housing  250 C is adapted to slidably fit within a bore of coupling  320 C. Seal  265 B is disposed at the juncture of housing  250 C and coupling  320 C. Seal  265 B has a T-shaped cross section in that a center rib is disposed between housing  250 C and coupling  320 C and a pair of flange legs are disposed on an inner wall of each of housing  250 C and coupling  320 C. In one embodiment, seal  265 B is fabricated of a rubber material or a low durometer plastic.  
         [0045]    Housing  250 C includes battery compartment  255  and recess  270  for receiving spring  275 B. Spring  275 B is a coil spring which encircles a portion of housing  250 C. Housing  250 C includes a recess  270  adapted to retain spring  275 B. Housing  250 C also provides a mounting surface for electrode  285 B. In the embodiment shown, four such electrodes  285 B are evenly distributed about the periphery of housing  250 C, however, numbers greater than or less than four are also contemplated. Each electrode  285 B includes conductive metal tab fabricated of aluminum sheet stock. A first leg of each electrode  285 B is bonded to housing  250 C with an adhesive. The second leg of each electrode  285 B is mounted to, and is electrically coupled with, circuit board  305 . In one embodiment, circuit board  305  includes a printed circuit board. Electrical circuitry and components are mounted on circuit board  305 . Piezoelectric transducer  315 A and transducer mounting panel  310  are affixed to circuit board  305 . In one embodiment, circuit board  305  includes a processor.  
         [0046]    Electrode  280 B, in the embodiment illustrated, is of a longer length than electrode  285 B and includes an inwardly curved portion at a lower end. Electrode  280 B is bonded to a electrode  285 B by a film of electrically disbonding adhesive  290 . Electrode  280 B is sufficiently flexible to allow the curved portion to deflect over catch  295 . Catch  295  is formed on an interior wall of coupling  320 C and is received in a matching hole of electrode  280 B. Sliding leaf interconnect  300 A establishes an electrical connection between an electrical conductor on circuit board  305  and electrode  280 B. Piezoelectric transducer  315 A is disposed beneath circuit board  305 , and in one embodiment, is mounted on stand-off  308 .  
         [0047]    [0047]FIG. 6B illustrates selected details of the embodiment of FIG. 6A. In the figure, circuit board  305  is affixed to electrode  285 B by machine screw and nut  395 . Electrode  285 B is in electrical contact with a first conductor of circuit board  305 . Electrode  280 B is bonded to electrode  285 B by electrically disbonding adhesive  290 . Electrode  280 B is also electrically connected to circuit board  305  by interconnect  300 A. Interconnect  300 A includes a flexible metal conductor. Interconnect  300 A is connected to a second conductor of circuit board  305  and is affixed by machine screw and nut  405 . A hole in electrode  280 B engages catch  295  of coupling  320 C. Spring  275 B urges separation of housing  250 C and coupling  320 C. Catch  295  prevents separation of housing  250 C and coupling  320 C provided that adhesive bond  290  remains strong. When bond  290  is weakened (by application of a voltage to electrode  285 B and-electrode  280 B), catch  295  retains electrode  280 B and electrode  285 B is carried away with the motion of housing  250 C.  
         [0048]    [0048]FIG. 7 illustrates a flow chart of method  350  for assembling remote unit  200 G. At  355 , electrode  280 B is bonded to electrode  285 B using an electrically disbonding epoxy resin adhesive. In assembling the embodiment of FIGS. 6A and 6B, four pairs of electrodes are prepared. At  360 , electrode  285 B of the electrode assembly is affixed to circuit board  305 . As illustrated in FIG. 6B, electrode  285 B is secured to circuit board  305  by a machine screw and nut however, other fasteners are also contemplated, including, for example, a rivet, a self-taping screw, adhesive or a mechanical clip. At  365 , piezoelectric transducer  315 A is affixed to circuit board  305 . Transducer  315 A, in one embodiment, is bonded using an adhesive however, other fasteners are also contemplated, including, for example, a clip or a mechanical fastener. At  370 , supply  260  is installed within a cavity of the housing. In the embodiment illustrated, two batteries are used for the supply, however numbers greater or less than two are also contemplated. At  375 , circuit board  305  is affixed to housing  250 C. In the embodiment illustrated, circuit board  305  is fastened to housing  250 C using a heat staked joint, however, other fasteners are also contemplated, including, for example, an ultrasonic weld, a machine or self-taping screw, a rivet, a clip or adhesive. At  380 , spring  275 B is positioned on a portion of coupling  320 C. Spring  275 B is received at surface  326  and urges separation of housing  250 C. At  385 , seal  265 B is positioned on a lip of coupling  320 C. Coupling  320 C, seal  265 B and housing  250 C are adapted to allow seal  265 B to remain affixed to housing  250 C and readily release from coupling  320 C when housing  250 C is separated from coupling  320 C. At  390 , the method continues with the assembly of housing  250 C onto coupling  320 C.  
         [0049]    [0049]FIGS. 8A and 8B illustrate views of remote unit  200 H according to one embodiment of the present subject matter. In the figure, housing  250 D includes a cavity to receive four batteries  262  and circuit board  305 . Circuit board  305  includes circuitry for receiving an electric signal from piezoelectric transducer  315 B and generating a voltage to release electrically disbonding adhesive  290 . Electrically disbonding adhesive  290  is disposed between electrode  280 C and  285 C. Piezoelectric transducer  315 B is affixed to circuit board  305  by stand-offs  318 . Piezoelectric transducer  315 B includes a piezoelectric element encased in a ported resonant chamber or housing. The port of the resonant chamber is positioned to expose the element to audio propagated in coupling  320 D.  
         [0050]    In one embodiment, coupling  320 D includes a length of PVC pipe. In one embodiment, coupling  320 D is approximately 18.5″ in length. Coupling  320 D includes lower portion  321 , slot  322 , thin wall section  323  and counterbore  324 , as shown in the detail view of FIG. 8B. Lower portion  321  is adapted for affixation to a scheduled plumbing pipe section. Spring  275 C is captivated at a first end by tab  282  of electrode  280 C and at a second end, by a surface of piezoelectric transducer  315 B. In one embodiment, spring  275  is of conical cross section. Electrode  280 C is secured to coupling  320 D by engagement of tab  319  with slot  322  and adhesive  284 . In one embodiment, adhesive  284  includes double-back tape. Thin wall section  323 , having a wall thickness less than that of lower portion  321 , provides clearance for insertion of electrode  280 C. Counterbore  324  provides clearance for a leg of seal  265 B. An electric circuit to provide a voltage across adhesive  290  is provided by electrode  285 C coupled to circuitry on circuit board  305  and by the series combination of electrode  280 C, spring  275 C and electrical interconnect  300 B coupled to circuitry on circuit board  305 . In one embodiment, interconnect  300 B includes a flexible conductive wire soldered to spring  275 C and soldered to circuit board  305 .  
         [0051]    In FIGS. 8A and 8B, electrodes  280 C and  285 C are shown extending upwards beyond the overall height of coupling  320 D. In one embodiment, electrode  285 C is adapted to extend downward into the bore of coupling  320 D and electrode  280 C is adapted to rise above slot  322  to a height approximately flush with a top surface of coupling  320 D. In this manner, following separation of housing  250 D, electrodes  280 C remain substantially within the bore of coupling  320 D following separation.  
         [0052]    According to one embodiment, assembly of remote unit  200 H includes inserting circuit board  305  and batteries  262  into housing  250 D. Electrode  285 C is captivated within housing  250 D by an adhesive joint or mechanical fastener within the cavity of housing  250 D. In addition, electrodes  285 C and electrodes  280 C are bonded together using electrically releasable adhesive  290 . A small diameter end of spring  275 C is positioned against a surface of piezoelectric transducer  315 B and a large diameter end of spring  275 C is captivated by tabs  282 . Next, an adhesive is applied to an exterior surface of electrode  280 C and housing  250 D is mated with coupling  320 D by inserting electrodes  280 C into the bore of coupling  320 D and engaging tab  319  with slot  322 .  
         [0053]    According to one application, coupling  320 D of remote unit  200 H is assembled onto vent pipe  100  using a standard or scheduled pipe coupling positioned below a roof line. Coupling  320 D is thus positioned to extend through the roof and allow unobstructed installation of a roof vent flashing.  
         [0054]    For one particular type of glue, the current flow required to sufficiently weaken the joint is a function of the thickness of the glue line. Consequently, a uniformly dimensioned glue line will have predictable and repeatable release characteristics. In one embodiment of the present subject matter, the distance between the electrodes determines the dimensional thickness of the glue line. In one embodiment, the electrodes are fabricated of sheet stock and the spacing between the electrodes is determined by molded features in the respective portions of the present subject matter. For example, in one embodiment, a first electrode is held captive by alignment features that engage the edges of the electrode. An amount of glue is deposited on the first electrode surface and a second electrode is brought into contact with the glue and held apart from the first electrode by molded spacers. In one embodiment, the first and second electrode are positioned with a predetermined spacing and a glue is injected in the void between the electrodes. In one embodiment, the spacing of the electrodes is established by means of molded bosses or shoulders formed in the electrode mounting area. In one embodiment, a shim or spacer is inserted between the electrodes and compressed to achieve a desired parallel spacing.  
         [0055]    [0055]FIGS. 9A, 9B,  9 C and  9 D illustrate different views of an embodiment for establishing a uniform glue line using a splined assembly. FIG. 9A illustrates housing  250 E and an electrode  285 D disposed atop each of three land areas. Three valleys  420  are shown interspersed between the lands. FIG. 9B illustrates coupling  320 E and an electrode  280 D disposed at the bottom of each of three valleys. Three land areas  425  are shown interspersed between the valleys. FIG. 9C includes a perspective view of coupling  320 E aligned for insertion into housing  250 E. In FIG. 9C, electrodes  285 D and electrodes  280 D are visible. FIG. 9D illustrates a sectional view through housing  250 E and coupling  320 E. Bond  290  is disposed between electrode  280 D and electrode  285 D.  
         [0056]    In one embodiment, the release mechanism of the remote unit includes a motor. A motor, as used herein, includes any device that physically displaces an armature in response to an electric current. In one embodiment, displacement of an armature of a solenoid triggers separation of the housing and the coupling. In one embodiment, an electromagnet is operated to trigger separation of the housing and coupling.  
         [0057]    [0057]FIG. 10 illustrates an exploded view of remote unit  200 J according to one embodiment of the present subject matter. In the figure, housing  250 F is adapted to receive seal  265 B, spring  275 B, supply  260  and release mechanism  410 . Release mechanism  410  includes a motor driven gear train for displacing dogs  415  relative to corresponding L-shaped slots  420  of coupling  320 F. Release mechanism  410  includes electronic circuitry and components for receiving a wireless signal. Upon receiving the wireless signal, dogs  415  are rotated about axis  90  in slots  420 . When dogs  415  have moved sufficiently far, spring  275 B urges separation of housing  250 F from coupling  320 F, thus breaking the airtight seal provided by seal  265 B.  
         [0058]    [0058]FIG. 11 illustrates a cross sectional view of remote unit  200 K according to one embodiment. In the figure, housing  250 G includes a cavity for batteries and electronic circuitry, here modeled as switch  455 . Switch  455  includes circuitry for receiving a predetermined release signal and applying a voltage to adhesive joint  290  in response to receiving the signal. Housing  250 G includes an angled base which matches an angle on coupling  320 G. In the embodiment shown in the figure, electrode  485  encircles at least a portion of a diameter of housing  250 G and electrode  480  encircles at least a portion of a diameter of coupling  320 G. In one embodiment, two or more electrode segments are distributed about a diameter of both housing  250 G and coupling  320 G. An electrical connection is established between supply  260  and electrode  480  by means of interconnect  465  and interconnect  475 . Interconnect  465  is affixed to housing  250 G by anchor  460 . Anchor  460  includes a heat staked plate however, other means of fastening are also contemplated, including for example, ultrasonic welding, rivet, screw or adhesive. Interconnect  465 , when assembled, establishes an electrical connection with contact  470 . Contact  470  is electrically coupled to electrode  480  by interconnect  475 .  
         [0059]    [0059]FIG. 12 illustrates an exploded detail view of a portion of housing  250 H and coupling  320 H. In the figure, housing  250 H includes conductive electrode  485 . Electrode  485  is aligned with adhesive  290  disposed in cavity  292 . Cavity  292  is sized to receive a film of electrically releasable adhesive and electrode  480  disposed at a bottom of cavity  292 . Seal  265 A is received by cavity  266  and cavity  264 .  
         [0060]    Electrically releasable adhesive  290  bonds housing  250 H to coupling  320 H. Seal  265 A provides an air-tight seal to allow testing of the vent system. When switch  455  of FIG. 11 is closed, electric current flows through interconnect  465 , contact  470  and interconnect  475  and provides a current through adhesive  290  by electrode  480  and electrode  485 . A voltage induced across adhesive  290  causes the adhesive to weaken. When sufficiently weak, gravitational forces urges housing  250 G to slide away from alignment with coupling  320 G and fall away from vent  100 . In one embodiment, a spring is positioned within remote unit  200 K to urge separation of housing  250 G and coupling  320 G. In the embodiments of FIGS. 11 and 12, the adhesive joint is undergoing a tension force when a positive air pressure is applied to the vent system.  
         [0061]    In one embodiment, an electrically releasable adhesive is disposed to directly hold the vent stop in a fixed position relative to the coupling and a seal positioned between the vent stop and coupling provides an airtight joint. In one embodiment, the electrically releasable adhesive is disposed to hold two or more structural elements in a fixed position relative to each other and when the adhesive is disbonded, a release mechanism is operated to allow the vent stop to be freely separated from the coupling.  
         [0062]    [0062]FIG. 13 illustrates an embodiment wherein an adhesively bonded joint is used to hold spring-loaded clips in position, thus securing the vent stop relative to the coupling. In the figure, electrode  710  and electrode  715  are fabricated of conductive metal strips and bonded together with electrically releasable adhesive  290  in the manner of a lap joint. Each end of extension spring  705  is coupled to a holding clip  720  by link  725 . The bonded electrode assembly of electrode  710  and electrode  715  is under a compression load applied by stretched extension spring  705 . Extension spring  705  urges holding clips  720  in a direction towards the interior of coupling  320 K. In one embodiment, extension spring  705  is fabricated of non-conductive material. In one embodiment, extension spring  705  is fabricated of a metal and includes an insulator portion to prevent shorting out electrode  710  and electrode  715 . Holding clips  720  are affixed to housing  250 K at an upper end and a tab formed at the lower end of holding clips  720  engages slot  322  on the interior wall surface of coupling  320 K. An airtight seal is provided by seal  265 A. Release springs  275 C are affixed to housing  250 K at a first end and contact a surface of coupling  320 K at a second end. Release springs  275 C are under tensional forces which urges separation of housing  250 K and coupling  320 K.  
         [0063]    Electrical circuitry not shown in the figure is adapted to provide an electrical current to electrode  715  and electrode  710  upon receipt of a release signal. The electrical current weakens the adhesive bond causing electrode  715  and electrode  710  to slide past each other under the compressive force from spring  705 . The contraction of spring  705  draws holding clips  720  from slot  322  and the extension forces from release springs  275 C urges separation of housing  250 K from coupling  320 K.  
         [0064]    Other embodiments are also contemplated wherein a weakened disbonding adhesive provides a trigger for the separation of a housing and coupling.  
         [0065]    In one embodiment, the housing is separated from the coupling upon receipt of a wireless signal. The wireless signal, according to one embodiment, includes an audio frequency signal propagated through the plumbing system. FIG. 14 illustrates piezoelectric transducer  31   5 A affixed to circuit board  305  by riser  490 . Riser  490  includes an annular mounting surface for affixing piezoelectric transducer  315 A to circuit board  305 . Riser  490 , in one embodiment, is fabricated of molded plastic. Piezoelectric transducer  315 A is positioned a distance of approximately ¼ wavelength away from circuit board  305  and an electrical signal is conducted using wires  495 .  
         [0066]    [0066]FIG. 15 illustrates local unit  600  for generating audio for triggering separation of the remote unit. In the figure, plug  605  includes external threads for engagement with internal threads of plumbing fitting  145 . Plumbing fitting  145 , in one embodiment, includes a clean out fitting and is installed in a convenient location within the plumbing system, as shown in FIG. 1. Piezoelectric transducer  610  is positioned within a cavity of plug  605  and displaced from the backwall of plug  605  by riser  615 . Piezoelectric transducer  610  is coupled to signal generator  620 . Signal generator  620  supplies an audio frequency signal which produces an audio signal within the plumbing system. In one embodiment, the generated audio signal has a carrier frequency of approximately3 kilo Hertz (kHz) and a modulation frequency of approximately 3 Hertz (Hz). In one embodiment, the generated audio signal has a carrier frequency greater or less than approximately 3kHz and a modulation frequency of greater or less than 3Hz. In one embodiment, plug  605  includes a portable power supply, such as, for example, a battery. In one embodiment, plug  605  includes a user operable switch for activating piezoelectric transducer  610 .  
         [0067]    In one embodiment, the audio signal is fully modulated at 100% and thus oscillates between a zero, or quiescent, level and a peak signal level. In one embodiment, the audio signal is modulated at a rate less than 100%.  
         [0068]    In one embodiment, plug  605  includes a power cord for coupling with a metered electric service. In one embodiment, the signal produced by signal generator  620  can be tailored to operate a particular remote unit selected from a plurality of remote units. In one embodiment, plug  605  can be installed in any fitting  145  shown in FIG. 1 and an audio signal will cause release of all remote units  200 A. In one embodiment, plug  605  can be installed in any fitting  145  shown in FIG. 1 and an audio signal will cause release of a predetermined remote unit  200 A.  
         [0069]    In one embodiment, the local unit is coupled to an exterior wall of a vent and an audio signal is propagated through the wall of the vent and into the interior or lumen of the vent.  
         [0070]    According to one embodiment, following testing of the DWV system using the present subject matter, local unit  600  is removed from fitting  145  and a standard plumbing plug is installed.  
         [0071]    Other embodiments of local unit  600  are also contemplated. For example, in one embodiment, a piezoelectric transducer is affixed to an unthreaded fitting. In one embodiment, the transducer is affixed to the plumbing system by a slip joint. In one embodiment, the transducer is affixed to a fitting adapted for a manual press-fit against a fixture or fitting of a plumbing system. For example, in one embodiment, the transducer is manually held in position at a plumbing fitting, a waste line p-trap or a toilet bowl.  
         [0072]    [0072]FIG. 16 illustrates a flow chart of method  625  for using the present subject matter. At  630 , the remote unit is armed for separation. In one embodiment, this entails manually operating an electrical switch on the remote unit to supply power to circuitry for monitoring the signal from the piezoelectric transducer of the remote unit. In one embodiment, the remote unit includes a manual switch coupled to a lanyard and when the switch is actuated, an indicator light is illuminated to indicate that the unit is armed. At  635 , the remote unit is installed on the plumbing vent. In one embodiment, this includes providing a coupling to the vent at a position below the roof line of the structure. With the remote unit in position and armed for separation, the plumbing system can be tested for leaks, as indicated at  640 . Leak testing may involve closing any rough-in openings and filling drains and p-traps with water. Following satisfactory testing, at  645 , the remote unit is separated. In one embodiment, this entails removing a standard plumbing plug from a clean out fitting and installing plug  600 . Plug  600 , in one embodiment, includes a portable power supply, a signal generator and a manually operable switch. When a suitable audio signal is generated within the plumbing system, the housing separates from the coupling of the remote unit. In the event that multiple remote units are installed, each remote unit separates independent of any other remote unit. At  650 , the separated housing is recovered. In one embodiment, the coupling and an electrode remain on the vent. In one embodiment, the separated housing can be fitted to a different coupling for another use. In one embodiment, the housing includes a generally spherical cover that facilitates recovery of the housing.  
         [0073]    In one embodiment, the release mechanism is armed prior to installing the remote unit on the plumbing vent. The remote unit produces an audible beep tone when armed.  
       Alternative Embodiments  
       [0074]    Variations of the above embodiments are also contemplated. For example, in one embodiment, the remote unit includes an infrared (IR) communication port and is adapted to receive an IR signal. Upon receiving an IR signal modulated with a predetermined signal, the remote unit provides a release signal to trigger the separation of the housing from the coupling. In one embodiment, the local unit includes a handheld transmitter which has an IR port. The IR port of the local unit is aimed in the general direction of the remote unit and a suitable signal is transmitted.  
         [0075]    In one embodiment, the remote unit includes an optical port adapted to receive an optically communicated signal from, for example, a laser light source.  
         [0076]    In one embodiment, the housing includes a signal generator and upon receipt of a signal to separate the housing and coupling, the remote unit generates and sounds an audible signal to acknowledge receipt of the release signal. Other distinctive sounds can be generated for other purposes. For example, upon arming, one embodiment renders an audible signal to confirm the mode of operation of the remote unit. In one embodiment, piezoelectric transducer  315  produces audio in response to a signal received from a signal generator coupled to housing  250 .  
         [0077]    In one embodiment, a wireless signal is communicated to the remote unit to trigger separation of the housing from the coupling. Other messages are also contemplated. In one embodiment, a wireless signal is communicated to the remote unit to disarm the remote unit. In one embodiment, current drawn from the remote unit power supply in the disarmed mode is lower than that drawn when armed.  
         [0078]    In one embodiment, the remote unit includes a wireless transmitter. In one embodiment, the wireless transmitter of the remote unit sends a signal in response to an inquiry signal received by the remote unit. In one embodiment, the wireless transmitter of the remote unit sends a signal according to a predetermined schedule. The wireless signal from the remote unit, according to one embodiment, includes the operational mode of the remote unit. In one embodiment, the wireless signal includes data corresponding to a condition or state of charge of the battery of the remote unit. In one embodiment, a message from the remote unit indicates that a release signal has been received but that an error condition exists which precludes separation of the housing. In one embodiment, the wireless message includes an error code.  
         [0079]    In one embodiment, the local unit includes a visual display panel. The display panel indicates data corresponding to a message received from the remote unit.  
         [0080]    In one embodiment, the wireless signal includes an audio frequency signal. In one embodiment, the remote unit includes microphone for receipt of an audio frequency signal. In one embodiment, the remote unit includes an audio speaker. In one embodiment, the microphone is sensitive to audio propagated external to the lumen of the vent.  
         [0081]    In one embodiment, the communication module includes a radio frequency (RF) receiver. In one embodiment, the communication module includes a radio frequency (RF) transmitter.  
         [0082]    In one embodiment, the remote unit includes a portable power supply and a manually operable switch coupled to the release mechanism. Activation of the manually operable switch triggers separation of the housing from the coupling. In one embodiment, the manually operable switch includes a lanyard. The lanyard is routed from the remote unit to a convenient location such as, for example, a nearby window or the ground. Upon activating the switch by pulling on the lanyard, the housing separates from the coupling.  
         [0083]    In one embodiment, the remote unit includes a release mechanism and a pair of wires having a first end connected to the release mechanism. The second end of the pair of wires is routed from the remote unit to a convenient location such as, for example, a nearby window or the ground. To release the housing, a power supply is coupled to the pair of wires.  
         [0084]    In one embodiment, the remote unit includes a portable power supply. In one embodiment, the portable power supply includes one or more batteries. In one embodiment, the portable power supply includes a solar power panel.  
         [0085]    In one embodiment, the release mechanism includes an electric motor operated gear train. For example, in one embodiment, the release mechanism includes one or more retaining pins that engage a mating surface and when the retaining pins are retracted, the housing is released from the coupling. In one embodiment, the motor includes an electric solenoid.  
         [0086]    In one embodiment, the disbonding adhesive includes a thermally releasable adhesive. Application of heat causes the thermally releasable adhesive to soften and release. In one embodiment, an electrical heater is actuated upon receipt of a signal from the communication module. In one embodiment, a chemical heater is actuated upon receipt of a signal from the communication module.  
         [0087]    In one embodiment, the disbonding adhesive includes an optically releasable adhesive. Exposure of the adhesive to a light having a particular characteristic, (i.e., a particular wavelength) causes the optically releasable adhesive to soften and release. In one embodiment, a light emitting diode (LED) is coupled to the housing and is illuminated upon receipt of a signal from the communication module. In one embodiment, an LED coupled to the housing indicates that the remote unit is armed.  
         [0088]    In one embodiment, the disbanding adhesive is affixed to one or more electrodes. In one embodiment, multiple adhesive joints are distributed about a diameter of the remote unit. For example, in one embodiment, two sets of electrodes (each with a film of disbonding adhesive) are distributed about the remote unit. More or less than two sets of electrodes are also contemplated. With multiple sets of electrodes, one embodiment provides that the sets of electrodes are uniformly distributed about a diameter of the remote unit.  
         [0089]    In one embodiment, a single spring is provided to urge separation of the housing from the coupling. In one embodiment, multiple springs, uniformly spaced, are provided to urge separation of the housing from the coupling.  
         [0090]    In one embodiment, the spacing between the piezoelectric element of the remote unit and a circuit board is greater or less than ¼ wavelength.  
         [0091]    In one embodiment, the housing, power supply, seal and spring is ejected from the vent upon release. In one embodiment, one or more electrodes are ejected with the housing.  
         [0092]    In one embodiment, the remote unit includes a manually operable electric switch. Actuation of the electric switch engages the circuitry to monitor signals received from the communication module. In one embodiment, the manually operable electric switch is connected to a lanyard. In one embodiment, the manually operable electric switch includes an insulative tab that separates a pair of contacts. In one embodiment, a light is coupled to the arm switch to indicate that the remote unit is in the armed mode.  
         [0093]    In one embodiment, the release mechanism includes an actuator to release the housing from the coupling. In one embodiment, the actuator includes a disbonding adhesive. In one embodiment, the actuator includes a motor. In one embodiment, the actuator includes a solenoid.  
         [0094]    In one embodiment, a wireless signal is communicated acoustically within the plumbing system. In one embodiment, the remote unit includes an actuator coupled to a wireless signal receiver. The actuator is coupled to an operable mechanical device or plumbing valve. Upon receiving the wireless signal, the mechanical device or a plumbing valve is manipulated by the actuator.  
         [0095]    In one embodiment, the ejected housing is recovered and discarded while the coupling remains on the vent. In one embodiment, the ejected housing is serviced and remanufactured using another coupling. In one embodiment, remanufacturing includes replacing the batteries, replacing the seal and testing the functionality of the communication module and release mechanism.  
         [0096]    In one embodiment, the release mechanism of the remote unit includes an energy storage device to urge separation of the housing from the coupling. In one embodiment, the energy storage device includes a spring. In one embodiment, the energy storage device includes a chemical compound that when catalyzed, a reaction occurs thus releasing energy. In one embodiment, the energy storage device includes a motor. In one embodiment, a positive atmospheric pressure is applied to the vent to urge separation of the housing and coupling.  
         [0097]    In one embodiment, an electrode includes aluminum. In one embodiment, an electrode includes copper. In one embodiment, an electrode includes stainless steel. In one embodiment, an electrode includes an electrically conductive material.  
         [0098]    In one embodiment, the housing includes acrylonitrile-butadiene-styrene (ABS) plastic. In one embodiment, the housing includes PVC plastic. In one embodiment, the housing includes a polymer material. In one embodiment, the coupling includes ABS plastic. In one embodiment, the coupling includes PVC plastic. In one embodiment, the coupling includes a polymer material. In one embodiment, the coupling is adapted for bonding with ABS or PVC plumbing pipe.  
         [0099]    In one embodiment, the number of springs differs from that of the number of sets of electrodes.  
         [0100]    In one embodiment, an electrode is fastened to the housing using a mechanical fastener. In one embodiment, an electrode is fastened to the housing using a threaded fastener. In one embodiment, an electrode is fastened to the housing using a clip. In one embodiment, an electrode is fastened to the housing using a heat staked joint. In one embodiment, an electrode is fastened to the housing using an ultrasonically welded joint.  
         [0101]    In one embodiment, the housing includes a substantially spherical structure adapted to facilitate recovery of the housing from a roof. In one embodiment, the spherical structure includes a soft foam structure with a cavity adapted to receive a housing. In one embodiment, the spherical structure is sized to reduce the likelihood of entrapment in a gutter or downspout.  
         [0102]    In one embodiment, the housing includes a first portable supply coupled to supply a voltage to the processor or circuitry of the present subject matter. In one embodiment, the housing includes a second portable supply coupled to supply a voltage to the disbonding adhesive of the present subject matter. In one embodiment, the housing includes an inductor and circuitry configured to supply a second voltage to the disbanding adhesive wherein the second voltage is greater than the first portable supply.  
         [0103]    In one embodiment, the housing includes a capacitor and circuitry configured to supply a second voltage to the disbanding adhesive wherein the second voltage is greater than the first portable supply.  
         [0104]    In one embodiment, an electrode is bonded to a circuit board by a screw. In one embodiment, an electrode is bonded to a circuit board by a press fit connection.  
         [0105]    In one embodiment, the processor includes one or more logic gates and circuitry adapted to generate a release signal in response to receiving a predetermined wireless signal. In one embodiment, the processor includes a microprocessor.  
         [0106]    In one embodiment, a disbanding adhesive provides both the holding force to prevent decoupling of the stop and also provides an air-tight seal for the plumbing system. In one embodiment, an air-tight seal is provided by an o-ring or gasket and the disbonding adhesive holds the stop to the coupling.  
         [0107]    As used herein, the term pipe includes plumbing pipes or tubes such as metal or plastic pipes use in DWV systems or supply lines. The term pipe also refers to gas piping. The term pipe also includes ductwork such as that made of sheet metal and typically used for heating, ventilating and air conditioning (HVAC) applications.  
       Conclusion  
       [0108]    The above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description.

Summary:
A wireless signal is propagated via a communication channel and received by a vent stop. The vent stop, upon receiving and decoding the signal, conducts an electric current to release the vent stop from a plumbing vent. In one embodiment, an intralumen audio signal is communicated to the vent stop and an adhesive joint securing the vent stop to the vent pipe is released upon passing an electric current through the joint. In one embodiment, an electric motor or solenoid releases the stop from the vent pipe. A spring or other energy storage device ejects the stop from the vent pipe following release.