Abstract:
A rotary matrix switch allows arbitrary selection from among different electrical connection configurations between m input terminals and n output terminals by rotation of a shaft or dial. A rotary shaft has a plurality of contact mechanisms at spaced locations and angular positions. The locations of the contact mechanisms correspond to individual contacts between the input and output terminals. The contact mechanisms may be lobes, indentations, conductive strips, or the like. Rotation of the shaft selectively engages ones of the contact mechanism to connect electrically various input and output terminals. The rotary shaft is removable to allow for the ability to make field upgrades and provide new configurations of connections. One embodiment of the invention can function as a telephone headset adapter, wherein rotation of a shaft allows the user to choose easily from among different handset port wiring configurations.

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates in general to apparatus for electrical switching between arbitrary numbers of input and output terminals, and in particular to the field of telephone headset adapters and the wiring configuration switching for compatibility with the various handset port interfaces. 
     2. Background of the Invention 
     In order to interface properly a telephone to a headset, a telephone headset adapter must correctly match the transmit and receive lines of the handset to the transmit and receive lines of the headset. To obtain broad product acceptance, the telephone headset adapter must be compatible with a large variety of telephones. However, a major problem in providing a telephone headset adapter that is compatible with most telephones is the lack of industry standards for handset port wiring. Most telephones use a four pin modular connector to plug in the handset. However, pin assignment for these four pins is not standardized. In addition, some manufacturers use a three wire interface with the fourth pin providing power for handset electronic systems. 
     Traditionally the connection between the headset and handset has often been achieved using either multi-pole bit switches or combinations of readily available, or custom built, slide switches. These solutions thus require the use of “codes” or switch setting combinations which are non-intuitive to the end user. The switches are typically small and difficult to manipulate with one&#39;s fingers, thus making it difficult for the user to configure correctly the telephone headset adapter. Furthermore, if the “code” is lost, misplaced, or unknown, the user has little recourse but to try different switch position combinations, cycling systematically through the different possibilities. For the average user this might be difficult to do. Clearly it would be advantageous for the user to be able to cycle quickly and easily through a range of possible combinations or configurations. 
     Another drawback is that most of the traditional switch solutions are only dedicated to a subset of possible combinations of handset and headset connections. As a result, when a new telephone wiring combination is needed for a new telephone a complete product redesign of the telephone headset adapter is required to adapt to the new wiring configuration. 
     Other traditional solutions include a silicon “crosspoint” switch chip that can connect any one of (typically) four input lines with any one of (typically) four output lines. This solution suffers from the drawback that extensive protection circuitry is required to prevent damage to the crosspoint switch from line voltages, RF interference and ESD events. Furthermore, if isolation between the telephone and the adapter system is required, power from the adapter system must be provided to the isolated telephone interface section of the circuit. This requires extra cost. Clearly it would be more cost effective to have an adapter system which is isolated from the telephone and which has a passive telephone interface section. 
     SUMMARY OF THE INVENTION 
     The present invention provides apparatuses for arbitrarily electrically connecting m input terminals with n output terminals with the use of a rotary matrix switch. Each apparatus can be used to connect some or all of the m input terminals with some or all of the n output terminals, leaving the remaining input terminals disconnected from the output terminals. A terminal can be, for example, a device to which a wire or a cable can be attached, or, for another example, merely an electrical junction that can be used to connect electrically a device with another device. One such apparatus for effecting arbitrary electrical connection comprises an assembly housing the m input and n output terminals, a number of electrical connectors (such as electrical spring contacts, for example) for connecting a number of the input terminals with a number of the output terminals, and a second assembly housing a rotary shaft having one or more contact mechanisms which can rotate with the shaft to engage or disengage selected ones of the electrical connectors. As the user rotates the rotary shaft, various ones of the contact mechanisms couple to selected predetermined ones of the electrical connectors, and thereby the apparatus cycles through various electrical connection configurations between the input and output terminals in a continuous and straightforward manner. 
     One embodiment finds use as an interface adapter between a telephone and a headset, thereby allowing the user easily to choose from among different possible handset wiring configurations. 
     The contact mechanisms can take a variety of different forms. For example, the contact mechanisms may be lobes, strips of electrically conductive material, indentations or depressions, or any other mechanism coupled to the rotary shaft which can mechanically or electrically engage two separated electrical connectors in response to rotation of a rotary shaft. 
     Further, the housing for the rotary shaft can be of monolithic construction, enabling easy assembly. The combined housing and shaft can be constructed so as to allow easy removal and replacement of the shaft should new wiring configurations dictate, thereby allowing for an unlimited number of configurations. This enables the shaft to be replaced with a new shaft by the user, thereby making the making field-upgrading of the apparatus, for example a telephone adapter, relatively quick and easy. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric drawing showing two assemblies, and a rotary shaft, of a rotary matrix switch apparatus. 
     FIG. 2 is an isometric drawing showing assembled apparatus, with a rotary shaft housed in a second assembly, and the second assembly connected to a first assembly. 
     FIGS. 3 a  and  3   b  are isometric drawings showing a rotary shaft from its different ends. 
     FIGS. 4 a - 4   b  are two cross sectional views of a rotary shaft, with certain details omitted for ease of understanding. 
     FIGS. 5 a ,  5   b , &amp;  5   c  present two plan views and one isometric view of a possible monolithic manufacture for a rotary shaft housing assembly. 
     FIG. 6 is a cross sectional view of another embodiment of the rotary shaft. 
     FIGS. 7 a  and  7   b  illustrate an alternate embodiment of the contact mechanisms. 
     FIG. 8 illustrates a telephone headset adapter with a first rotary shaft, and a second, different rotary shaft. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is an isometric drawing of one embodiment of the present invention. A first base assembly  100 , made of an electrically insulating material pad, such as plastic, houses four input terminals  101  and sixteen output terminals  102 . In this embodiment the four input terminals are in the form of four separated electrically conducting strips of material arranged sequentially along a first line on the pad. From each of the four input terminals  101  are electrically connected and project four equal length arcuate strips  103  of electrically conducting material. Each strip  103  is arced so that the free end, not fixed to the input terminals  101 , is raised above and not in electrical contact with part of one of the sixteen output terminals  102 , and so that if a base-directed force is applied to the strip  103 , the strip swings about the fixed end, toward the pad, so as to touch and come into electrical contact with one of the output terminals  102 . If the force is subsequently removed the strip  103  moves away from, and thus electrically disconnects from, the output terminal  102 . The strip  103  thus functions as an electrical spring contact. The free end of each of the strips  103  is bent to form a contact area  104 . Thus the strip  103  can come into solid electrical contact with one of the output terminals  102 . Those skilled in the art will recognize that the electrically conducting strips  103  need not be arcuate: this feature of the embodiment shown in FIG. 1 does, however, provide the advantage of displaying a greater restorative force against a displacing lobe. Straight strips, for example, might also be used. 
     In each of the apparatuses there are n output terminals. In the embodiment shown in FIG. 1 there are sixteen output terminals  102  in the form of sixteen separated electrically conducting strips of material arranged sequentially along a second line which is parallel to the first line. The exact shape of the sixteen output terminals is not important. In general it may depend on the use intended for the switch. For example, for some uses one can envisage output terminals  102  possessing an electrical linkage through the base assembly  100 , rather than lying on the base assembly  100  as shown in FIG.  1 . In the embodiment shown in FIG. 1 one end of each output terminal  102  is approximately the same size and shape as one of the bent free ends  104  of the strips  103 , so that efficient electrical contact is made when the strip  103  swings down to make contact with the output terminal  102 . The other end of the output terminal  102  juts out and cannot come into physical contact with the strip  103 . This permits a wire to be soldered to the other end. 
     The rotary matrix switch functions as a switch between input and output terminals. One skilled in the art will recognize however that the notion of input and output terminals may be interchanged uniformly throughout without loss of generality. Use of the word “terminal” suggests electrical connection with some external device. In the embodiment shown in FIG. 1 each of the four input terminals  101  and each of the sixteen output terminals  102  is such that it can be electrically connected to a different wire. In the case of the output terminals  102  the electrical wire connection will occur at the end of the terminal that does not come into contact with the strip  103 , as described above. Further, for an application of a preferred embodiment to the field of telephone headset adapters (where four input wires are to be configured to connect with four output wires), the output terminals  102  corresponding to the first strip  103 , on each input terminal strip  101 , will be electrically connected to the same wire, as will those corresponding, respectively, to the second, third, and fourth strips  103  on each input terminal strip  102 . This will effectively allow the rotary matrix switch to arbitrarily electrically connect any of the four input terminals  101  to any of the four output terminal wires. 
     Also shown in FIG. 1 is a second assembly  105  housing a rotary shaft  106 , both of which are made of electrically insulating material. The second assembly has a number of convex anchor tabs  107  which can fit into concave slots  108  in the first assembly  100  so as to bring the second assembly  105  into secure physical contact with the first assembly  100 . A possible manufacture for the second assembly  105  is shown in different views in FIGS. 5 a ,  5   b , &amp;  5   c , and will be described below. The various anchor tabs  107  are also shown in FIGS. 5 a ,  5   b , &amp;  5   c.    
     The rotary shaft  106 , when housed in the second assembly  105 , is fixed so that its only motion in general is to rotate about its longitudinal axis. The shaft has a number of contact mechanisms which selectively engage or disengage the strips  103  in response to rotation of the rotary shaft  106 . In this embodiment, the contact mechanisms are lobes  109  projecting out from the axis of the shaft  106 . The lobes  109  are positioned at various angular positions around the circumference of the shaft  106 , and at various distances along the length of the shaft  106 . The width of a lobe  109  is approximately that of one of the strips  103 . The lobes  109  are also shown in FIGS. 3 a ,  3   b ,  4   a , &amp;  4   b . FIGS. 4 a  &amp;  4   b  provides cross sectional views through the rotary shaft  106  at two different distances along the shaft: through the shaft  106  at a distance where two lobes  109  project in different directions (FIG. 4 b ), and through the shaft  106  at a distance where there are no lobes (FIG. 4 a ). For simplicity the lugs  110  and the circular base of the dial  115  are not indicated in FIGS. 4 a  &amp;  4   b . Note in FIGS. 4 a  &amp;  4   b  that the bulge  116  does not project from the shaft axis as much as does a lobe  109 . Each lobe  109  functions so that, as the shaft  106  rotates through various angular positions, the lobe  109  turns first to come into contact with and then away from exactly one of the strips  103 . During the time the lobe  109  is in contact with a strip  103  the lobe  109  exerts a force on the strip  103  so as to cause the strip  103  to swing towards and come into contact with the corresponding output terminal  102  on the base pad  100 . With the strip  103  thereby engaged, the corresponding input  101  and output terminals  102  become electrically connected. Further rotation of the shaft  106  causes the lobe  109  to disconnect from the strip  103 . The strip  103  thus moves away from the output terminal  102 , thereby disengaging, and electrically disconnects the corresponding input and output terminals. Note from FIGS. 4 a  &amp;  4   b  that, as the shaft  106  rotates, the bulge  116  will swing by its corresponding strip  103  and not engage it. Note also from FIGS. 4 a  &amp;  4   b  that in the embodiment shown there can be at most four lobes  109  (as well as a bulge  116 ) on any cam. Thus, in the embodiment shown there will be four different connection configurations between the input terminals  101  and output terminals  102 , each associated with a particular angular position of the shaft. Those skilled in the art will recognize that it is possible to construct and use a rotary shaft  106  with varying maximal numbers of lobes  109  on any cam, thereby correspondingly varying the number of different connection configurations between input terminals  101  and output terminals  102 . 
     The shaft  106  and second assembly  105  are constructed so that in at least one angular position of the shaft  106  the shaft is removable from the second assembly  105 . Referring to FIG. 1, in one embodiment this feature is provided by two tracking lugs  110 , projecting from the shaft, which permit the shaft to track easily in and out of the second assembly along guide tracks  111  in the second assembly. The tracking lugs  110  and tracks  111  in the second assembly  105  are such that, when the shaft  106  is fully housed in the second assembly  105 , the tracking lugs  110  no longer sit in and are guided by the tracks  111 , but rather are free to move, with the rotation of the shaft  106 , in the wells  112  in the second assembly  105 . As the shaft  106  is slid along the guide tracks  111  so as to be fully housed in the second assembly  105 , the locking lugs  113 , which also project from the shaft  106 , pass through the keyhole opening  114 . When the shaft  106  is fully housed in the second assembly  105  it can only be removed if the locking lugs  113  are aligned so as to pass through the keyholes  114 . There may be one or more orientations of the shaft  106  for which the locking lugs  113  are so aligned. The rotary shaft  106  is constructed so that, for at least one such orientation, none of the lobes  109  are in contact with any of the strips  103 . As shown in FIGS. 4 a  &amp;  4   b , when this occurs, each bulge  116  is at or near its point of closest approach to the strips  103 . With the lobes  109  and strips  103  thereby not in contact, the rotary shaft  106  can thereby be easily removed from the assembly  105  without damaging either the lobes  109  or the strips  103 . This allows quick and easy replacement of the shaft  106  with another similar shaft, having different lobe positionings, should circumstances dictate. This feature is useful if the desired input-output connections cannot be effected by the housed rotary shaft, and thus a new shaft with the proper lobes may be easily installed. For example, this situation may obtain where the rotary matrix switch is used in a telephone headset adapter, if new telephones, requiring new handset port wiring configurations, enter the market, and upgrading of the headset adapter is desired without redesign of its circuitry. 
     FIG. 8 illustrates this example, showing a telephone headset adapter  80  and first rotary shaft  82  and second rotary shaft  84 . The shafts have different configurations of lobes  86 , each shaft thus providing a different set of handset port wiring configurations when coupled with the second assembly (internal to the headset adapter  80 ). 
     At the opposite end of the shaft  106  from the locking lugs is the dial  115 , which facilitates manual rotation of the shaft  106 . 
     FIG. 2 is an isometric drawing of the assembled apparatus, showing the rotary shaft  106  fully housed in the second assembly  105 , which is in turn in secure physical contact with the first assembly  100 , as described above. 
     FIGS. 5 a ,  5   b , &amp;  5   c  show two plan and one isometric views of a possible monolithic manufacture for the rotary shaft housing second assembly  105  shown in FIG.  1 . FIG. 5 b  shows the various anchor tabs  107 , as well as the guide tracks  111  and wells  112  shown in FIG.  1 . The monolithic manufacture of the second assembly  105  offers ease of manufacture, for example, using  2 -part injection molding. Assembly into the second assembly is effected by swinging the end  118 , shown in the plan view in FIG. 5 c,  toward the end  119  so that the various segments of the second assembly  105  pivot about the two hinges  117 , and hooking end  118  in place around end  119 . FIG. 1 shows an isometric view of end  119  so hooked into place. As a result, the entire rotary switch apparatus may be manufactured with just three basic parts: the first base assembly, the shaft, and the second housing assembly. This further reduces the product cost and simplifies the manufactory process. 
     FIG. 6 illustrates a cross-sectional view of another embodiment of the present invention. Here, rotary shaft  156  has one or more curved contact mechanisms  139 , each of which has a strip  135  of electrically conductive material bonded to portion of its perimeter. A simple to manufacture version of this embodiment would be a rotary shaft  156  with a cylindrical surface, with various strips  135  of electrically conductive material placed at various locations and angular positions along the length of the shaft 
     Adjacent the shaft  156  ate two electrical connectors  137 , which couple to respective input  101  and output terminals  104 . The ends  131  of the connectors are curved to match the curvature of the contact mechanism  139 , and are separated by a gap between them. As the rotary shaft  156  is rotated through various angular positions, the strip  135  will come into contact with both ends of the pair of connectors  137 , completing the electrical connection and engaging the input and output terminals. 
     FIGS. 7 a  and  7   b  illustrate yet another embodiment of the contact mechanisms within the scope of the present invention. Here, instead of using lobes to engage the connectors, as in the embodiment of FIG. 1 a lobe  143  disengages connectors, and an indentation  159  is used to engage the connectors. More specifically, the rotary shaft  156  has a substantially circular lobe  143  with one or more indentations  159 . Selected ones of the connectors  157  have a bent portion  141  which generally is sized and shaped to fit within the indentation  159 . A connector with the bent portion is biased toward the rotary shaft  156 , either by tension in the connector itself, or by spring underneath the connector  157  (not shown). In the position of the rotary shaft  156  shown in FIG,  7   a,  the lobe pushes the bent portion  141  down, and disengages this connector  157  from its mating connector  157 . Further rotation of the shaft  156  aligns the indentation  159  with the bent portion  141 , allowing the connector  157  to rise and engage with its mating connector  157 , thereby coupling the respectively input and output terminals coupled to the connectors  157 . 
     Accordingly, as can be seen from the various embodiments, the rotary shaft and the contact mechanisms of the present invention are susceptible to many different embodiments, which produce the benefits and features of the invention. Accordingly, the present invention encompasses any rotary shaft having contact mechanisms which electro-mechanically engage or disengage selected, predetermined electrically connectors in response rotation of the rotary shaft.