Abstract:
A connection system for providing multiple modes of electromagnetic connection to a device. This system includes a ribbon cable with a plurality of multi-mode electromagnetic conductors arranged in a serial array, one alongside the other including a central optical conductor disposed between a pair of electrical conductors. The system also includes a multi-mode electromagnetic connector, that includes a housing, and optical transducers disposed between a pair of electrical terminals that have insulation piercing free ends. A cover that latchingly engages the housing applies pressure to the ribbon cable, forcing the ribbon cable to be pierced by the upper ends of the terminals and pressing the optical conductor into optical communication with said transducers. The electrical conductors carry electrical power comprising alternating current, at a frequency ranging between 10 and 30 kHz.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention pertains to cable and connector systems, which accommodate different types of electromagnetic signals, and in particular to optical and electrical signals. 
     2. Description of the Related Art 
     Modern signal and power bus systems, i.e., remote sensing and control technologies are becoming increasingly popular with the advent of digital circuitry and communication techniques. Analog, hard-wired forerunners to these technologies may be found in commercial locations where business needs require an isolated data bus within the facility to provide a LAN for communication or monitored for intrusion or fire. In these types of systems, electrical signals sent by a variety of detectors are transmitted over dedicated cable pairs of a traditional telephone system. Although, attempts have been made to couple various types of detectors with a common cabling of metallic conductors, a need still exists for efficient multi-mode cabling systems, compatible with modern communication systems. 
     SUMMARY OF THE INVENTION 
     The present invention provides a cable and connector system for accommodating both optical and electrical modes of electromagnetic communication. Cable and connector systems according to principles of the present invention provide a reduction in site installation costs. Preferably, a cable carrying both optical and electrical conductors is assembled in the form of a flat configuration often referred to as a “ribbon cable” configuration. The cable and connector system allows simple cost effective cable installation and module connection at various points to the multimode, i.e., optical and electrical buses provided by the cable. Preferably, the electrical bus provides power for modules such as distributed modules of a communication system or other sensors, distributed throughout the installation site. Data is carried by the optical conductor which operates as an optical data bus linking the installed modules. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of an installation site according to principles of the present invention; 
     FIG. 2 is a top plan view of a cable and connector system according to principles of the present invention; 
     FIG. 3 is a cross-sectional view taken along the line  3 — 3  of FIG. 2; 
     FIG. 4 is a cross-sectional view of a multi-mode connector making optical and electrical connector making optical and electrical connection to the cable; and 
     FIG. 5 is a cross-sectional view similar to that of FIG. 4 but showing a connector arrangement in which the optical conductor is deformed. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, and initially to FIG. 1, a site location is generally indicated at  10 . The present invention has found immediate application for use in a commercial radio site controller installation. Included is a radio antenna  14  on tower  15  operated under control of supervisory systems located within a housing structure  20 . The housing structure  20  accommodates equipment and personnel and is suitable for operation in a relatively remote environment. Those skilled in the art will readily appreciate that the present invention could also be employed with other types of site locations, such as residential dwellings and commercial structures, such as those located in an urban business district. 
     Indicated in FIG. 1 is cable  30  interconnecting a number of modules including a GPS receiver  32 , a temperature alarm  34  and a door alarm  36  and a tower top communication module  17 . The cable  30  provides a connector system for signal distribution such as site time/frequency reference and site diagnostic signals, such as those transmitted by alarm  34 . In addition, other modules could be added to sense power outages as well as the environmental temperature module  34  environmental conditions, such as humidity, and the presence of water indicating a flooding condition. Modules could also sense the presence of certain predefined gases present in housing  20 . In the preferred embodiment, signals from the various modules are carried cable  30  throughout the site location and are resolved or converted for transmission on an outgoing conventional telecommunications T-1 line  40 . 
     According to one aspect of the present invention, it is preferred that the data signals be communicated in an optical domain or mode. As will be seen herein, cable  30  includes an optical conductor for the data. As contemplated herein, the term “optical conductor” includes virtually any media for transmitting optical signals. Included are various types of light pipe material such as glass, fiberglass, LEXAN materials, and polycarbonate or other polymeric compositions. Cable  30  constructed according to the principles of the present invention is preferably flexible so as to conform to bends which are common to most cabling installations, particularly installations within a building structure. Accordingly, it is preferred that all of the components of the cable, including the optical conductor contribute to the flexible bending ability of the cable. Although rigid optical conductors could be employed in some instances, it is generally preferred that the optical conductors be made of a flexible or bendable material, such as polymeric and other “plastic” materials. Optical signals carried by bus  30  are converted at site control and converter module  44  for transmission along T-1 line  40 . It is generally preferred that bus  30  and the optical circuit associated therewith be used for local service at the installation site and that the T-1 line or other conventional communication be used for transmission to a location remote from the installation site. 
     Turning to FIG. 2, a portion of cable  30  is illustrated. In it&#39;s preferred form, cable  30  includes a centrally located optical conductor, light pipe, optical fiber, light guide or other optical conductor designated at  50 . Optical conductor  50  transmits optical signals in a preferred bandwidth of approximately 10-100 MHz. Referring to FIG. 3, the optical conductor  50  is enclosed in an outer, flexible sheath  52  formed of suitable flexible dielectric material such as plastics and plastic compositions. Disposed on either side of optical conductor  50  are conventional metallic conductors  54  of solid stranded or braided copper wire or other conventional construction. If desired, a plurality of electrical conductors can be disposed to one side of the optical conductor, with provision for the additional electrical conductors being made in the multi-mode connector described below. In FIG. 2, portions of sheath  52  have been removed for illustrative purposes to expose the interior optical conductor  50  and the outer metallic conductors  54 . 
     As with the optical conductor  50 , metallic conductors  54  carry electromagnetic signals. However, it is preferred that metallic conductors  54  carry power signals and that data signals are restricted to optical conductor  50 . Power for the modules  32 ,  34  and  36  mentioned above with respect to FIG. 1 receive power from electrical conductors  54 . It is generally preferred that the modules include respective power transformers with the electrical conductors  54  transmitting higher frequency alternating current power signals, substantially higher than 60 Hz, so as to reduce the size and weight of power transformers associated with the modules serviced by cable  30 . Although it is desired that power conductors  54  transmit alternating current power, they could also be employed to carry direct current power if such is desired due to special site considerations. 
     In the preferred embodiment, alternating current power signals carried by electrical conductors  54  operate at a frequency between 5 and 50 kHz, and most preferably in a range between 15 and 30 kHz. It is generally preferred that substantially higher frequencies are not employed for power distribution in order to limit the effects of radio frequency interference with surrounding equipment. However, if desired substantially higher frequency power signals can be employed if interference is not a problem. It is generally preferred that modules serviced by cable  30  receive power through transformer coupling for a more efficient electrical power distribution in addition to avoiding ground potential gradients, as well as surges induced for example by lightning strike. 
     In carrying out the present invention, it is generally preferred that contact is made to electrical conductors in cable  30  without breaking the cable and that contact is made to both optical and electrical conductors without requiring elaborate termination connectors. As shown in FIG. 2, the cable portion is illustrated in conjunction with two connectors  60 . Referring to FIG. 4, connector  60  includes metallic terminals  62  having upper ends  64  of a fork configuration for piercing portions of sheath  52  surrounding metallic conductors  54 . Terminals  62  are constructed according to conventional insulation piercing or insulation displacement techniques. Electrical connections to terminal  62 , not shown in the figure, are provided in a conventional manner. If additional electrical conductors are provided by cable  30 , a corresponding number of additional insulation displacing terminals are provided, each terminal constructed according to the manner illustrated. 
     In FIG. 4, access has been gained to optical conductor  50  for optical coupling with optical transducers  70 ,  72 , which are preferably mounted within a common body  74 . In FIG. 4, a locking cap  78  lockingly interengages connector sidewalls  80  in a manner, which maintains downward pressure on the cable components, especially the optical conductor. For example, inner fingers  82  press down on the sheath material immediately above electrical connectors  54 , forcing the forked ends  64  of terminal  62  to pierce the sheath, with the forked ends coming into electrical contact with electrical conductors  54 . A central inner finger  86  pushes either directly or indirectly on the top of optical conductor  50  causing the bottom portion of the optical conductor to maintain optical communication with transducers  70 ,  72 . The transducers  70 ,  72  in turn are connected to external circuitry not shown in the figure. 
     Turning now to FIG. 5, a multi-mode connector  100  and optical conductor  110  are shown. Multi-mode connector  100  is in several respects similar to multi-mode conductor  60  described above with reference to FIG.  4 . One difference is the inclusion of a longer central finger, designated at  102 , dimensioned so as to distort the relaxed cross-sectional shape of optical conductor  104 . Preferably, optical conductor  104  is made of a material which more readily deforms under pressure, causing the optical conductor to take on the generally oval shape illustrated in FIG.  5 . This changes the angle of contact between the lower surface of the optical conductor and the transducers  70 ,  72  causing contact angles closer to 90° than the arrangement illustrated in FIG. 4 where the optical conductor remains virtually undistorted from its relaxed, circular cross-sectional shape. If necessary, the walls  80  of the connector can be shortened to insure the desired compression of the optical conductor. 
     Several variations are contemplated. For example, FIGS. 1-4, show electrical conductors  54  totally encapsulated by sheath material. Referring to FIG. 4, the distance between the outer surface of optical conductor  50  and the electrical conductors  54  can be reduced such that the optical conductor itself provides the majority of the dielectric insulation between the electrical conductors. In those applications where the optical circuitry is not excessively degraded, the forked ends  64  of terminal  62  can make direct contact with the lateral surface portions of the optical conductor. As can be seen in the cross-sectional view of FIG. 4, it is generally desired that the diameter of optical conductor  50  be substantially greater than the diameter of electrical conductors  54 . Assuming that penetration of terminal  62  into the laterally opposed sides of optical conductor  50  is not objectionable, the portions of sheath  52  between electrical conductors  54  and optical conductor  50  can be significantly reduced or eliminated. It is generally desirable that sheath  52  surrounds both the optical conductor and the electrical conductors as indicated in FIG. 3 in order to fix the multi-mode (i.e., optical and electrical) conductors in the desired flat or ribbon cable geometry. It should be noted that while the optical conductor provides electrical insulation for the outer electrical conductors  54 , in a mechanical sense the outer electrical conductors provide mechanical shielding or protection for the more sensitive optical conductor. When arranged in the preferred flat or ribbon cable arrangement, the overall cable construction can be easily curved and bent to follow practical site installation constructions. 
     In application, the modules are provided with the multi-mode connectors  60  or  100 , with cable  30  running continuous, and unbroken through the various modules. The cover or latch  78  of the connector is removed and the cable is positioned in the manner indicated in FIGS. 4 or  5 . The cover then is inserted to apply downward pressure to the cable causing the optical and electrical multi-mode connections between the cable and the modules being serviced. Thus, a connector system is provided which allows quick attachment to the bus cable by a simple compression latch similar to that of existing insulation displacement of electrical connectors. The inner fingers are provided to apply pressure on top of the optical conductor, opposite the location of optical transducers  70 ,  72 . The inner fingers provide contact between the bottom side of the optical conductor and the transducers as is needed to optical signal communication between the transducers and the optical conductor. With the present invention, substantial savings in site cabling and surge suppression costs can be employed with a cabling and surge suppression system having a data portion immune to EMI transients and a power system which does not produce RF interference. 
     While the principles of the invention have been described above in connection with a specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention.