a typical power line communication system for implementing features of the invention is shown in fig1 . a high voltage ( hv ) power line 102 transmits power through sub - station 104 to a medium voltage ( mv ) power line 106 that eventually may connect through a transformer 108 to low voltage ( lv ) lines 110 that provide alternating electrical power to customer premises 111 , 112 , 113 . a wireless connection through transceiver 107 may provide an alternative connection to customer premises 109 . a head end data network provides communication signals 120 via a fiber optic cable or other suitable transmission links to the end user customer premises 111 , 112 , 113 using power line cables as the transmission medium . techniques for converting data signals to the electrical domain for transmission via the power lines are well known . a transmitter contains a modulator which modulates the incoming data onto a carrier signal using well known rf modulation techniques . as described above , typical carrier frequencies for a power line communication system are in the range of 1 - 30 mhz . the modulated signal is provided to the power line cable 106 via couplers 122 . it will be understood by those skilled in the art that a signal on an optical cable must first be converted to an electrical signal , then reformatted ( demodulated - remodulated ) to a format appropriate for transmission on a power line ( e . g ., ofdm ). such a modulated and reformatted signal can then be coupled by the present invention onto a power line as shown at coupler connections 122 . a power line communication system of the type shown in fig1 may use orthogonal frequency division multiplexing ( ofdm ) in which the available bandwidth is split up into multiple narrowband channels which do not interfere with each other . however the present invention is applicable to any type of power line communication system such as ofdm , a spread - spectrum system , etc . thus , in accordance with any appropriate bpl system , broadband signals are carried over the mv line 106 and optionally lv lines 110 to receivers at the customer premises 111 , 112 , 113 , or via mv line 106 through wireless transceiver 107 to customer premises 109 . for purposes of the present description , it is assumed that the mv power line cable 106 will typically supply power at 4 - 66 kv . such medium voltage cable is typically an aluminum cable having a 1 cm diameter . couplers 122 provide an interconnection for the modulated carrier signal to the mv line 106 . various types of couplers are known in the art , including for example inductive couplers and capacitive couplers . the carrier signal is transmitted along the length of mv power line cable 106 through transformers 108 to lv lines 110 . the low voltage power line typically supplies power at 100 - 240 volts . the low voltage line transmits the data signals to the customer premises 111 , 112 , 113 where a modem demodulates the signal and extracts the data message . it is noted that for ease of description only downstream ( i . e ., from head end to end user ) data transmission is shown and described . one skilled in the art would readily recognize that upstream transmission could be accomplished in a similar manner . as described above in the background section , there is a significant problem with safety risks in providing broadband coupler connections directly to an energized power line . as shown in the embodiment of fig1 , the mv line 106 may connect through mv couplers 124 to signal repeater electronics 126 . providing a repeater connection to a mv power line is an important application in some embodiments of the invention . the mv line 106 may also connect through mv coupler 128 via bypass router 130 to lv coupler 132 in order to achieve data signal transfer to an lv power line 110 . router 136 interconnects with lv power line 110 at lv coupler 134 in order to selectively deliver appropriately addressed data signals to receivers at either customer premises 112 or customer premises 113 . the coupler installation of the invention can be incorporated at high risk mv coupler connection 128 , and also at lower risk lv coupler connections 132 , 134 , although installation at these lv points does not pose the high safety risk associated with installation on mv lines the mv line 106 may also connect through mv coupler 142 via bypass router 144 to lv coupler 146 in order to achieve data signal transfer to an lv power line 110 . router 140 interconnects with mv power line 106 at mv coupler 138 in order to selectively deliver appropriately addressed data signals via wireless transceiver 107 to customer premises 109 . using such a wireless transceiver , as for example a wifi access point , makes it unnecessary to provide a transformer bypass path for the broadband signal . the coupler installation of the invention can be incorporated at high risk mv coupler connections 138 , 142 , and also at lower risk lv coupler connection 146 . fig2 is a high level schematic diagram showing exemplary locations for installing a coupler device on a power line communication system . although most present day power lines transmit alternating current ( ac ), the invention is applicable to both ac and dc ( direct current ) power line systems . utility poles 220 support mv lines 202 and lv lines 204 at a safe distance from the ground . implementing a communication system on the power lines typically requires electronic components 206 , 208 , 210 , 214 , 216 including capacitors 212 , 218 in order to assure satisfactory transmission of broadband signals to customers 224 . the invention provides a safe , secure and reliable coupling technique for making electrical interconnections to high risk mv lines at coupling locations 220 , as well as to lower risk lv lines at coupling locations 222 . the embodiment of fig3 shows an exemplary coupler device 300 having an insulated portion 302 and a conductive portion 304 connected through link 306 via capacitor 308 to electronic components 310 . a threaded sleeve 312 receives a conductive adjustment screw 313 with threads 314 . the adjustment screw 313 has a contact point 316 for electrical contact with a power line cable ( not shown ). an insulated tool 320 , as for example a tool known in the trade as a hotstick , includes a long extension 322 having a cap 324 sized and shaped for engagement with the adjustment screw 313 . an installer can grasp a handle 326 at a location remote from high risk mv or lower risk lv power cables and actuate the tool such as by rotation in direction 328 . the insulated portion 302 of the coupler 300 may have a hook - shaped end 334 formed by extension 330 and truncated end 336 . a leg portion 332 provides an attachment junction with the conductive portion 304 . the overall contours of the insulated portion 302 may be u - shaped in order to provide multiple interior contact surfaces 338 , 340 , 324 for contacting adjacent surfaces of a power line cable in order to support the coupler when the adjustment screw 313 is in open position , as well as to securely establish electrical contact and maintain attachment to the power cable when the adjustment screw 313 is in closed position . other hook - like shapes may be incorporated in the insulated portion 302 in order to partially surround the power cable and maintain the coupler 300 in self - supporting position during initial coupler installation as well as during actuation of the tool to accomplish electrical contact between the conductive portion 304 and the energized power cable . of course , the benefits of the invention can be achieved with other adjustment members which perform a similar function to the adjustment screw 313 so that the coupler can have a conductive component remotely actuated from a retracted position to a forward conducting position while the coupler remains in self - supporting position on the power cable . it will be understood by those skilled in the art that various angular orientations of a coupler fixture and its conductive element relative to a power line cable are possible in order to achieve the goals of the present invention . for example , in fig4 a , a conductive adjustment screw 404 has a tapered head 406 with a central contact point 408 and is shown facing upwardly in a vertical direction for making electrical contact with power cable 400 . a coupler having contact surfaces approximately coincident with plane 410 will apply compressive forces in a direction 412 in order to help maintain such electrical contact and hold the coupler in secure position on the power cable . a conductive adjustment screw 414 has a tapered head 416 with a central contact point 418 and is shown facing laterally in a horizontal direction for making electrical contact with power cable 400 . a coupler having contact surfaces approximately coincident with plane 420 will apply compressive forces in a direction 422 in order to help maintain such electrical contact and hold the coupler in secure position on the power cable . a conductive adjustment screw 424 has a tapered head 426 with a central contact point 428 and is shown facing partially upwardly in a somewhat oblique angular direction for making electrical contact with power cable 400 . a coupler having contact surfaces approximately coincident with plane 430 will apply compressive forces in a direction 432 in order to help maintain such electrical contact and hold the coupler in secure position on the power cable . similar orientations are illustrated in fig4 b for non - tapered heads respectively having sharp peripheral edge contact surfaces 438 , 448 , 458 . compressive forces applied perpendicular to planes 410 , 420 , 430 will maintain electrical contact with adjustment screws 436 , 446 , 456 respectively , and hold the coupler in secure position on the power cable . referring to fig5 a and 5b , a coupler device is shown in closed position with a conductive portion in electric metallic contact with a power line cable 400 . in these embodiments , a u - shaped insulated coupler arm 334 includes an elongated extension 330 and a shortened extension such as truncated end 336 . an adjustment shaft in the form shown as threaded adjustment screw 313 makes electrical contact and also applies compressive forces to hold the power line cable 400 in secure position against the u - shaped insulated coupler arm 334 . in fig5 a a central contact point 316 on the apex of the adjustment screw 313 makes the electrical contact . in fig5 b a sharpened circular peripheral edge 416 on the apex of the adjustment screw 31 makes the electrical contact . various other shapes and type of sharp contact edges or points may be used in order to penetrate any weather coating or other surface material on the power line cable and make the appropriate metallic contact for transmitting message and control signals between the coupler and the power line cable . additional embodiments for facilitating engagement of a self - supported coupling device on a power line are shown in fig6 a and 6b . referring to fig6 a , an insulated arm 600 includes elongated extension 602 , header 604 and shortened extension 606 which together form a rectangular - shaped hook having a central concave recess 608 shaped and sized to provide support on a power line cable 611 . a threaded conductor shaft 613 is shown in partially closed position with its tapered head 615 starting to penetrate an outer insulation layer prior to making electrical contact with the power line cable 611 ( see fig4 a ). referring to fig6 b , an insulated arm 610 includes shortened extension 612 , header 614 and elongated extension 616 which together form a rectangular - shaped hook having a triangular slot 618 to provide support on a power line cable 611 . the threaded conductor shaft 613 is shown in partially closed position similar to fig6 a . referring to the embodiment of fig7 , a mechanical fixture assembly includes a coupler device 740 shown in a self - supporting position on a power line 700 , and also includes a remotely activated insulated tool 722 that has been manually engaged with the coupler device 740 . the insulated tool 722 has a cap 724 sized and shaped to fit an enlarged base 726 of a threaded shaft 728 on the coupler device 740 . after an installer has manually rotated a handle 727 remotely located from the power line 700 in order to advance the threaded shaft 728 forwardly , a sharpened point 730 on an apex of the shaft advances from a partially closed position making initial contact with an insulation layer as shown in the drawing until the insulation layer is penetrated and electrical metallic contact is made directly with the power line ( see fig4 a ). the threaded shaft and its adjacent threaded base 732 together constitute a conductor portion of the coupler device for carrying signals to and fro between line 734 and power line 700 . in this embodiment , an insulated arm is formed by a first extension 742 connected at its lower end to the base 732 , and is joined at its upper end 748 to angular extension 744 to form a triangular recess 745 for supporting the coupler device on the power line 700 . a lower leg portion 746 on the angular extension 744 along with interior contact surfaces 750 , 752 help to assure the coupler device 740 remains in self - supporting position on the power line 700 upon initial installation of the coupler device and during adjustment of threaded shaft 728 into conducting position by insulated tool 722 . in view of the foregoing description and drawings of exemplary embodiments , it will be understood by those skilled in the art that variously shaped coupler devices with differently shaped interior contact surfaces can be utilized in order to maintain the coupler device in a somewhat stable self - supporting position on a power cable during the various stages of installation . in some instances , the corresponding mass of each portion of the exemplary coupler devices shown in the various drawing figures may if necessary be counter - balanced in order to help the coupler device remain self - positioned , such as when an adjustment member such as a threaded shaft is in retracted open position as well as when an adjustment member is moved into closed position such as during rotation of the threaded shaft by the remotely positioned installer . referring to the embodiment of fig8 , a power line 800 is shown in an engaged position with a closed fully installed coupler device 840 comprising another mechanical fixture . a conductor shaft 820 has an upper end 822 tapered to form a sharpened central point 824 , the shaft being formed integral with a conductor plate 826 connected to signal line 828 . a separate bolt 830 that may be formed with a dielectric material has a threaded upper end 836 that engages a matching threaded sleeve 838 on a u - shaped insulated arm 840 . rotation of the bolt by a remotely activated tool ( not shown in this drawing ) advances the conductor plate 826 and conductor shaft 820 forwardly into closed position to provide electrical metallic contact of the central point 824 with the power line 800 , as shown in the drawing . rotation of the bolt 830 is facilitated by a raised low - friction boss 834 on the underside of conductor plate 826 . when the conductor plate is moved to a closed position as shown by arrow 846 , the insulated arm 840 has a lower leg 842 abutting an end 844 of the conductor plate 825 in order to eliminate an initial installation gap . when the coupler device is in open position as shown in phantom at 848 , the initial installation gap allows insertion of the power line 800 inside of the u - shaped insulated arm . the upper part of the u - shaped insulated arm 840 provides a recess for holding the coupler device in self - supporting position on the power line 800 . in view of all the foregoing , it will be understood by those skilled in the art that various embodiments of the invention enable and facilitate implementation of a broadband communication system on energized power lines by various installation methods including but not limited to one or more of the following techniques : making multiple connections to power lines through individual coupler devices in order to bypass transformers connecting lv customer premises to shared power lines ; or making multiple connections to power lines through wireless transceivers in order to connect customer premises to shared power lines ; or making multiple connections to power lines through capacitive coupler devices in order to connect customer premises to shared power lines ; or connecting repeater electronics to mv power lines in order to facilitate broadband signal transmission on shared power lines to customer premises ; or connecting routers to lv or mv power lines in order to direct delivery of data messages to appropriate customer premises . the foregoing detailed description is to be understood as being in every respect illustrative and exemplary , but not restrictive , and the scope of the invention disclosed herein is not to be determined from the detailed description , but rather from the claims as interpreted according to the full breadth permitted by the patent laws . it is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention .