WO1996029759A1

WO1996029759A1 - Add-on mtu assembly for use in a telephone subscriber junction box

Info

Publication number: WO1996029759A1
Application number: PCT/US1996/000536
Authority: WO
Inventors: Harry M. Capper; Sam Denovich; William J. Garver; Maris A. Glass; Michael P. Green; James W. Robertson
Original assignee: The Whitaker Corporation
Priority date: 1995-03-17
Filing date: 1996-01-17
Publication date: 1996-09-26
Also published as: AU4657196A

Abstract

An add-on MTU assembly (10) for a binding post array of a telephone junction box to interpose an MTU circuit unit between subscriber wiring and the utility's distribution cable. A first module (40) includes an MTU circuit unit (60, 290) therein having tip and ring wires (70, 72) extending to terminal housing subassembly (100), and having binding post wires (74, 76) extending to be attached to binding posts (20, 22). Terminal housing subassembly (100) includes a pair of terminals (112, 114) terminatable to ends of subscriber tip and ring wires (24, 26), and terminals (112, 114) are also electrically connected with tip and ring wires (70, 72) extending to the first module (40). Each of the modules (40, 100) includes a binding post clamp (44, 104) to be clamped onto a respective binding post (20, 22). The add-on assembly (10) is compact and flexible to be added onto a binding post array along with like others for other pairs of binding posts and fit into a confined space immediately surrounding the binding post array.

Description

ADD-ON MTU ASSEMBLY FOR USE IN A TELEPHONE SUBSCRIBER JUNCTION BOX ^"

This relates to the field of telecommunications and more particularly to interconnections of telephone subscriber lines to distribution cable.

Interconnecting of a subscriber to the telephone utility's network wiring generally includes interconnecting a drop wire cable both to the subscriber's premise wiring at a network interface device (NID) and to the distribution cable of the telephone utility.

Interconnection of the drop wire cable to the premise wiring is generally performed in an NID enclosure outside or inside the building housing the subscriber's premises, and such enclosure may provide for interconnections of several subscriber lines within the same building.

Interconnecting the pair of conductors of a drop wire cable to the distribution cable is generally performed in a junction box adjacent the distribution cable such as on a pole or aerially hung from the distribution cable, and commonly many such interconnections are made in each junction box, involving many such drop wire cables which may be one-pair or six-pair cables.

One manner of establishing the interconnections of the two individual conductors of each subscriber cable is through the use of a pair of binding posts. Each binding post of the pair is electrically connected to a respective conductor of the distribution cable for either the tip or ring circuit. An upstanding threaded shaft of each binding post permits an exposed end of either the tip or ring circuit of the subscriber cable to be wrapped tightly therearound; alternatively a ring tongue terminal terminated onto the conductor is clamped tightly to the binding post by a nut threaded onto the shaft. The electrical connections to the binding posts preferably allow untermination and retermination for ease of service and repair. Arrays of binding post pairs are generally spaced very closely together within each junction box to minimize the overall size of the junction box without substantially impeding the ability of telephone service personnel to manipulate wire ends for termination to the binding posts.

Upon determination of interrupted service to a particular subscriber, telephone service personnel must inspect the interconnections of the subscriber's drop wire cable to the distribution cable as well as the interconnections of the subscriber's drop wire cable to the indoor premise wiring at the NID, all in order to determine the location of the fault and subsequent correction. If the location of the service interrupting fault is determined to be on the subscriber side of the NID, the subscriber is generally responsible for correcting the fault. If the fault is located along the network cable, repair and servicing involves different, more involved procedures, techniques and equipment than does the repair and servicing of drop wire cables.

Recently telephone utilities have initiated use of MTUs, or maintenance termination units, in an effort to enable fault location. Generally located in the NID, an MTU is dedicated to the particular subscriber line along which it is mounted; and in conjunction with signals from a remote test center the MTU can determine whether a line fault is on the subscriber side of its location, or on the utility or network side.

An MTU contains a pair of bilateral voltage-sensitive switches placed in the tip and ring conductors of the unit having a predetermined threshold of voltage and current, and a distinctive termination is provided across the tip and ring conductors so that subscriber-side open circuits can be determined, with the distinctive termination consists of a polarity-sensitive DC tip-to-ring leakage. When an applied test voltage is below the threshold voltage, the switch is in an "off" state and presents a very high impedance to the test system conducted remotely from the central office of the telephone utility. The application of a DC test voltage that is greater than the threshold voltage causes the switch to switch to an "on" or "low" impedance state. Tests made from the test system using a DC test voltage that is greater than the threshold voltage will operate the switch if there is a fault on the subscriber side of the MTU, and hence locates the fault as being on the subscriber side. A subsequent test made at a test voltage that is less than the threshold voltage will "see" only up to the MTU but not beyond. There is disclosed in US-A-5,175,662 a device that provides an MTU and a surge protector in a single package.

It is desired to enable remote electronic determination of the location of the fault prior to on- site inspection and repair.

It is further desired to secure maintenance termination units within junction boxes along the network distribution cable in order to determine whether the location of a fault is along the distribution cable or along the drop wire cable, prior to dispatch of telephone service personnel to the subscriber's premises from the central office.

The present invention is an assembly containing a maintenance termination unit and adapted to be secured to a pair of associated binding posts in a junction box already installed and in service. A first module is adapted to be releasably clamped onto an end portion of a first binding post; an MTU device is contained within a housing of the first module, and to its electrodes are terminated first ends of a pair of first conductor wires exiting the module. A second module also adapted to be releasably clamped onto an end portion of a second binding post of the associated pair, contains a pair of electrical terminals terminated to second ends of the pair of first conductor wires and thus to circuits of the MTU in the first module. The second module is adapted to provide for termination to tip and ring wires of a drop cable entering the junction box, and preferably utilizes apertures for wire end insertion and subsequent rotary movement of cylindrically shaped terminals by an actuator to establish assured electrical connections with the respective inserted wire ends through insulation displacement. Completing the assembly is a pair of second conductors exiting from the first module and provided with terminals adapted to be terminated easily onto the respective first and second binding posts for the tip and ring circuits respectively, after which the first and second modules may be clamped onto end portions of the first and second binding posts. The assembly of the present invention thus provides a complete self-contained MTU package for a subscriber, adapted to be easily and quickly installed in the junction box with minimal procedural steps.

It is an objective of the present invention to provide an add-on assembly of an MTU to an existing in- service junction box for subscriber interconnection, to provide test electronics permitting interrogation of fault location from the central office.

It is another objective to provide such an add-on assembly in a junction box having an array of closely spaced binding posts, to permit remote determination of the location of a subject line fault being along the network cable or on the subscriber's particular wiring including the drop cable. It is a further objective to provide such an add-on assembly of minimal size to occupy minimal space within a closely confined binding post array, to a selected pair of binding posts in a manner permitting other like assemblies to be installed on the remaining binding post pairs also within such close confinement.

It is an additional objective to provide such an add¬ on assembly that is easily removable for repair and replacement or to permit access to the binding posts for servicing. Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings. FIGURE 1 is an isometric view illustrating an add-on MTU assembly of the present invention after installation on a pair of binding posts of a telephone junction box;

FIGURE 2 is an exploded isometric view of a terminal housing of the MTU assembly;

FIGURE 3 is a partially exploded isometric view of the MTU assembly from below thereof, illustrating MTU module assembly and MTU conductor installation into the terminal housing of FIGURES 1 and 2; FIGURE 4 is an enlarged partial view of the bottom of the terminal housing after installation of the MTU conductors;

FIGURE 5 is a cross-sectional view of the terminal housing after MTU conductor installation, with one of the terminals positioned for insertion;

FIGURE 6 is an isometric view from below of another embodiment of terminal housing subassembly having a different binding post clamping section;

FIGURES 7 and 8 are isometric views of another embodiment of MTU module having a different, movable binding post clamping section, with FIG. 8 illustrating an arrangement of terminating the tip and ring MTU wires and the binding post wires to the MTU unit;

FIGURE 9 is an isometric view of another embodiment of terminal subassembly for use with an MTU module, having post sections similar to binding posts for connection of wire ends thereto; and

FIGURES 10 and 11 are additional embodiments of add¬ on MTU assemblies of the present invention. Add-on MTU assembly 10 is adapted to be used with a binding post block 12 having pairs of terminal sites 14 having binding posts 16, all assembled to a housing block 18. MTU assembly 10 is shown installed on binding posts 20,22 of a pair associated with a particular subscriber line represented by tip and ring subscriber wires 24,26 of a drop cable that extends to the subscriber's premise wiring (not shown) . Nuts 28 are used with each binding post for securing ring tongue terminals thereonto to establish electrical connections of conductor wires with the binding posts, and the binding posts in turn are electrically connected to respective conductors of the distribution cable of the telephone utility's network (not shown), as is conventional.

Add-on MTU assembly 10 includes a terminal housing subassembly 100 and an MTU module 40, with tip and ring MTU wires 70,72 extending therebetween and electrically interconnecting respective terminals of the terminal housing subassembly 100 and the MTU circuit within MTU module 40, as seen in FIG. 2. Also seen are binding post wires 74,76 electrically connecting the MTU circuit in series with the tip and ring subscriber wires 24,26 and the corresponding binding posts to complete the interconnection of the subscriber to the network. Housing body 102 of terminal housing subassembly 100 includes a binding post clamping section 104, and module housing 42 similarly includes a binding post clamping section 44, providing an integral mechanism to be physically secured to exposed lengths of binding posts 20,22 following termination of binding post wires 74,76 with binding posts 20,22 using spade terminals 78 crimped onto ends of binding post wires 74,76 and binding post nuts 28. Terminal housing subassembly 100 is seen to have wire- receiving apertures 106,108 for receipt of insulated, unterminated end portions of subscriber tip and ring subscriber wires 24,26 for termination therein.

Referring to FIG. 2, terminal housing subassembly 100 includes housing body 102, actuator 110, cylindrical terminals 112,114, annular insulative separator 116 and base cover 118. Cylindrical terminals 112,114 are insertable sequentially into annular cavity 120 into housing body 102 from top face 122 to surround center post 124 in interference fit therewith by being C-shaped and being expanded in diameter by center post 124, with insulative separator 116 inserted into annular cavity 120 in position between terminals 112,114. Actuator 110 is then inserted into annular cavity 120, with terminal- engaging section 126 partially surrounding terminals 112,114 and having a vertical rib 128 disposed in seam 130 of each terminal and seam 132 of separator 116 aligned therewith. Vertical rib 128 will serve to engage adjacent edges of terminals 112,114 to rotate the terminals during actuation for termination of subscriber wires 24,26.

With reference to FIG. 3, MTU module 40 includes module housing 42 having a board-receiving cavity 46 thereinto, and MTU unit 60 is insertable into cavity 46 following termination to electrodes thereof of first ends 80,82 of tip and ring MTU wires 70,72 and first ends 84,86 of binding post wires 74,76 such as by soldering. MTU unit 60 is shown to be of the type having a circuit board 62 and various electrical and electronic components 64 mounted thereonto and appropriately interconnected by board circuitry to conductors of MTU wires 70,72 and of binding post wires 74,76 and to each other. One method of termination of MTU wires and binding post wires to the circuit card of the MTU unit is shown in FIG. 8. A cover member 48 is secured such as by bonding with adhesive or ultrasonic welding beneath module body 42 to secure MTU unit therein, and provides an opening 50 defining a wire exit. A test port 52 provides for receipt of a test probe such as an alligator clip to engage MTU wire 72 routed appropriately along the MTU unit with module body 42 to be adjacent test port 52, thus permitting circuit integrity testing for the ring circuit of the MTU assembly 10 after installation. Terminal housing subassembly 100 provides a test port for testing of the tip circuit. Preferably a conformal coating of dielectric material is applied to the MTU unit, as is conventional to protect the components and circuits of the unit. Alternatively, upon insertion of MTU unit 60 into board-receiving cavity 46, potting material may be injected into cavity 46 for protection against moisture. As is seen in FIGS. 3 and 4, second ends 88,90 of tip and ring MTU wires 70,72 are positioned for insertion into respective passageways 134,136 into bottom face 138 of housing body 102 of terminal housing subassembly 100. First passageway 134 extends upwardly through center post 124 to top end 144 thereof. Second passageway 136 is in communication with annular cavity 120 and is aligned with a lower groove portion 140 (FIG. 5) generally aligned with an upper groove portion 142 (FIG. 2) extending vertically along an outwardly facing surface of center post 124 from the top end 144 thereof; insulative material separates the upper and lower groove portions (FIG. 5) . Insulation has been removed from second ends 88,90 to expose lengths of the conductors of MTU wires 70,72. Stripped second end 90 of ring wire 70 is inserted into associated passageway 136 into annular cavity 110 and disposed along the lower groove portion along center post 124. Second end 88 of tip wire 70 has a stripped length about twice as long as that of ring wire 72 and is inserted into respective passageway 136 and outwardly of top end 144 of center post 124 and is then bent back, entering annular cavity 120 and into upper groove portion 140, concluding at a location spaced and insulated from the end of second end 90. Tab 180 of upper terminal 112 is positioned adjacent test port 182 into actuator 110 to be engaged by a test probe such as an alligator clip to permit testing of the circuit integrity of the tip circuit of add-on MTU assembly 10.

In FIG. 4, bottom face 138 of terminal housing subassembly 100 is shown having channels 148 coextending laterally from entrances to passageways 136,138 and faired thereinto, along which insulated portions of tip and ring MTU wires 70,72 extend following full insertion into housing body 102. Pairs of opposed ribs 150 preferably establish a compression fit with the insulated wires for temporarily securing wires 70,72 to housing body 102 until base cover 118 is assembled to bottom face 138. Following full insertion of tip and ring MTU wires 70,72 into housing body 102, base cover 118 is then secured onto bottom face 138 of housing body 102. Short posts 152 may be force-fit into corresponding holes 154 into bottom face 146 to self-retain cover member in place, if desired. Alternatively, base cover 118 may be secured by being bonded in place by adhesive, or by ultrasonically welding. Following complete insertion of second wire ends 88,90 into housing body 102, lower terminal 114 is inserted into annular cavity 120 frictionally engaging both portions of second end 80 of tip MTU wire 72 extending partially beyond the surface of center post 124 from grooves 140,142, and then entering into frictional engagement similarly with second end 88 of ring MTU wire 70 as lower terminal 114 is fully inserted into annular cavity 120 until abutting the bottom thereof. Insulative separator 116 is then similarly inserted into annular cavity 120 around center post 124 to rest atop lower terminal 114. Upper terminal 112 is similarly inserted into annular cavity 120 in frictional engagement with both portions of second end 88 of tip MTU wire 72 until seated atop insulative separator 116. Finally, actuator 110 is inserted into annular cavity 120 with vertical rib 128 between seams 130,132 of upper and lower terminals 112,114 and insulative separator 116 as previously described, until collar 146 is seated in widened entrance 156 along top face 122 of housing body 102. Actuator 110 includes a protruding lug 158 for tool-assisted actuation thereof to rotate upper and lower terminals 114,112 during termination of subscriber wires 24,26. Referring now to FIGS. 2 and 5, terminals 112,114 each have a pair of opposed wire-receiving holes 160 through which ends of tip and ring subscriber wires 24,26 will pass after inserted through respective apertures 106,108 of housing body 102, through clearances 162 in actuator 110, through respective apertures 164 of center post 124 and into bores 166 into the cavity sidewall opposite wire-receiving apertures 106,108. Termination slots 168 of terminals 112,114 extend laterally from wire- receiving holes 162 and are dimensioned to be-just less than the diameter of the conductors of subscriber wires 24,26 in order to cut through the wire insulation and establish assured electrical engagement with the conductor therewithin during termination. This termination method permits easy untermination for repair and servicing, and easy re-termination subsequently. Terminal housing subassembly 100 may be filled with gel-like sealant material for protection of exposed metal of the terminals and wires from moisture.

Also seen in FIG. 5 is binding post clamp 104 of housing body 102, having a pair of semicylindrical arms 168 extending to respective free ends 168,170 spaced apart at gap 172, with arms 168 defining therebetween a cylindrical opening 174 for receipt of a binding post thereinto. A tapered lead-in 176 is defined at the entrance to cylindrical opening 174 to assist in placement of terminal housing subassembly 100 onto a corresponding binding post. Cylindrical opening 174 is dimensioned to have a diameter less than the outer diameter of a binding post, so that arms 168 are deflected outwardly upon bearing engagement of inner surfaces 178 thereof with the binding post. Semicylindrical arms 168 are integrally joined to housing body 102 and are designed to be rugged and durable to maintain clamping pressure on the binding post after placement thereon, and also permit removal therefrom if desired. Binding post clamp 44 of MTU module 40 (FIGS. 1 and 2) is similarly constructed. The add-on MTU assembly is exceedingly flexible in that the two portions joined only by tip and ring MTU wires allows various configurations in positioning of the terminal housing subassembly and the MTU module, and adapts to limited distances in binding post spacing. A plurality of such assemblies may be closely packed within the confinement of walls of the enclosure surrounding the binding post array in the junction box, which is desired to be as compact as possible.

FIG. 6 discloses another embodiment of terminal housing body 200 having a binding post clamp 202. Two positions 204,206 are defined by binding post clamp 202 for clamping onto a binding post, with a slot 208 extending toward the housing body from an end 210. Effectively a pair of opposed stiffly resilient arms 212,214 are defined coextending from housing body 200, and with pairs of arcuate clamping surfaces 216,218 opposing each other at each position 204,206 to clamp onto an end of a binding post received therebetween from below thereof as arms 212,214 are deflected slightly apart. The pair of positions permit the terminal housing subassembly to be positioned closer or farther from a binding post for greater flexibility in positioning in confined enclosures for binding post arrays, in addition to being angularly positioned as desired about a binding post through a range of about 100° or so to accommodate close spacing of adjacent add-on MTU assemblies used with adjacent pairs of binding posts.

Another advantage of the embodiments of FIGS. 1 to 6, and also those of FIGS. 7 to 9, is that the add-on MTU assembly of the present invention may be clamped onto a pair of binding posts other than the particular pair to which electrical connections are being made. For example, in an array of 25 pairs of very closely spaced binding posts where 5 pairs are not being utilized and are idle, and those 5 pairs are at one end of the array, if an add- on assembly is slightly larger than a particular binding post pair's associated confined space, MTU assemblies may be clamped onto their particular associated binding posts for the first five pairs, then the next pair of binding posts will remain undamped leaving a physical clearance between MTU assemblies and its own MTU assembly will then be clamped to the seventh binding post pair, with succeeding MTU assemblies clamped onto the binding post pairs preferably next in sequence; similarly, the twelfth and eighteenth binding post pairs will remain-undamped again for physical clearance; finally, MTU assemblies for the eighteenth, nineteenth and twentieth pairs will be clamped onto respective ones of the idle five pairs at the end of the array. Such flexibility in each add-on MTU assembly is provided by the use of binding post wires of appropriate length to electrically connect with the associated binding posts, so that physical clamping need not occur with the binding posts with which electrical connections must be made. Similarly, such staggering may be utilized where idle binding post pairs are located elsewhere in a particular array.

FIG. 7 illustrates another embodiment of MTU module 250 of the present invention. Module body 252 includes a slot 254 extending along side surface 256 from insertion face 258 and closed at the end thereof, with opposed slide rails 260 defined along opposed edges of slot 254 and with a back wall 262 closing off the interior of module body 252. A binding post clamp member 264 is shown that is assembled into slot 254 from insertion face 258 and includes flanges that cooperate with slide rails 260 to permit clamp member 264 to be selectively positioned along slot 254 for module body 252 to be positioned as desired for close spacing with adjacent module bodies of adjacent add-on MTU assemblies associated with adjacent pairs of binding posts in a closely spaced binding post array in a closely confined enclosure. A cover 266 is shown secured to insertion face 258 after insertion of MTU unit within module body 252, and serves to retain clamp member 264 onto module body 252, with tip and ring MTU wires 268,270 and binding post wires 272,274 extending outwardly from module body 252 at wire exit 276. Binding post clamp member 264 defines a pair of stiffly resilient arms 278 that define two positions for clamping onto a binding post, as in FIG. 6. Module body 252 also is shown to include a test port 280 along top face 282 at a first end 284 for insertion of an alligator clip prong (not shown) for testing of the ring wire circuit of the MTU assembly. Module body 252 also is shown to include a recess 286 in second end 288 of top face 282, defining a clearance for a prong of an alligator clip inserted into a test port of an adjacent MTU module (not shown) of an adjacent add-on MTU assembly if positioned in abutment with module body 252 in a close spacing.

FIG. 8 illustrates one manner in which the ring MTU wire may be configured to be terminated to the MTU unit 290 of MTU module 250 of FIG. 7 to be engaged by a test probe. End 292 is inserted through a slot 294 of the circuit board of the MTU unit and an elongated stripped portion is bent back to be soldered to a circuit of the circuit board. After MTU unit insertion, cover 266 is secured to insertion face 258 thus retaining MTU unit in module body 252. The elongated stripped bent back portion is positioned at an endmost edge of the circuit board adjacent the test port 280. Also seen in FIG. 8 is a pair of opposed guide slots 296 extending along inner end walls of module body 252 to cooperate with edges of the circuit card to facilitate card insertion into cavity 298 and also serving to secure MTU unit in position following assembly-

Another embodiment of terminal subassembly 300 is shown in FIG. 9, comprising a pair of conductive shafts 302,304 having exposed sections 306,308 extending from an insulative body 310 preferably molded about ends of the conductive shafts, or alternatively is at least securely affixed thereto. Insulative body 310 spaces apart and insulates the embedded shaft ends, which preferably include antirotation devices such as embossments 312 that cooperate with surrounding material of insulative body 310 to prevent rotation of the shafts. Insulative body 310 also includes a said binding post clamp 314 integrally molded thereon or securely affixed thereto, with binding post clamp 314 being similar to that of FIG. 7 or optionally similar to that of FIGS. 1 to 5. Preferably exposed shaft sections 306,308 are threaded and are of the same diameter as binding posts 16, and pairs of nuts 318 are disposed on respective exposed shaft sections 306,308 enabling clamping to stripped ends 34,36 of at least the subscriber tip and ring wires 24,26. Tip and ring MTU wires 268,270 may have spade terminals 78 terminated thereonto just as with binding post wires 272,274 extending from MTU module 250 of FIGS. 7 and 8, and with binding post wires 74,76 of FIG. 3. The terminal housing bodies of FIGS. 1 to 9, and the MTU module bodies, may be molded of thermoplastic material such as VALOX 420 SCO glass-filled polybutylene teraphthalate resin sold by The General Electric Company of Pittsfield, Massachusetts. Insulative spacer 118 of FIGS. 2 and 5 may be of polytetrafluoroethylene, or high- density polyethylene where relatively low process temperatures are involved for injection of conventional grease sealant materials into the terminal housing body, or of a copolymer of polyvinyl chloride. MTU units are commercially available from Texas Instruments such as Model No. 3MU and proposed Model No. 6MU. Similar MTU circuits are also used in a 5-pin Protected MTU Module Model No. 7AB6A, Commodity Code No. 107098196 sold by A T & T. The add-on MTU assembly of the present invention may be varied to complement a binding post array that is less confined both in binding post spacing and in the walls of the enclosure immediately therearound. FIG. 10 illustrates embodiment 400 of add-on MTU assembly of the present invention wherein the MTU and terminals associated with subscriber tip and ring wires are combined in a single module 402 having a binding post clamp. Assembly 400 as shown is adapted to clamp onto and electrically engage one binding post, while having one binding post wire 404 extending to the other binding post of the pair. The add-on MTU assembly 400 may have portions 406,408 acting as caps that enclose and cover the exposed portions of the pair of binding posts, and may also have binding post conductors that define electrical connections with the binding posts within the caps.

Further, FIG. 11 illustrates another embodiment of add-on MTU assembly 500 comprised of a single module having a pair of binding post receptacles containing conductive clamps (not shown) for clamping onto and electrically engaging both of the binding posts of the pair, and having two terminal housing portions 502 each having a single wire-receiving aperture 504 for receipt thereinto of either the tip or ring subscriber wire.

Other variations and modifications are possible in providing an add-on MTU assembly that are within the spirit of the invention and the scope of the claims.

Claims

WE CLAIM:

1. An add-on MTU assembly (10,400,500) for an array of binding posts (16,20,22) in a telephone junction box for interconnecting subscriber tip and ring wires (24,26) to corresponding conductors of a distribution cable and interposing an MTU circuit unit (60,290) in series in the tip and ring circuits, comprising: a first section (40,250) containing the MTU circuit unit (60,290) ; a second section (100,200,300) containing first and second terminals (112,114) for termination to subscriber tip and ring wires (24,26), said second section (100) adapted to permit electrical connection with said subscriber tip and ring wires (24,26) to respective ones of said first and second terminals (112,114); conductors (70,72) interconnecting said first and second terminals (112,114) to said MTU circuit unit (60,290) ; conductors (74,76) extending from said MTU circuit unit (60,290) to terminals (78) for establishing electrical connections with respective ones of a pair of associated binding posts (20,22); and at least one clamp section (44,104,202,264,314), each said at least one clamp section adapted to clamp onto an exposed end portion of a respective one of said pair of associated binding posts (20,22), whereby an assembly is defined for being installed onto a selected pair of binding posts (20,22) of an array thereof.

2. An add-on MTU assembly as set forth in claim 1 wherein a pair of test ports (52,182,280) are defined permitting testing of circuit integrity of tip and ring circuits within the assembly (10) .

3. An add-on MTU assembly as set forth in claim 1 wherein said first and second sections are portions of an integral housing body, and said integral housing body includes a wire (404) defining a binding post conductor

- lb and joining a cap member (408) adapted to cover a binding post (16,20,22) after said wire (404) is terminated to the binding post.

4. An add-on MTU assembly as set forth in claim 1 wherein said first and second sections are discrete first modules (40,250) and second modules (100,200,300), and said first and second terminals (112,114) of said second section are electrically connected to said MTU circuit unit (60,290) in said first section (40) by lengths of discrete first and second wires (70,72).

5. An add-on MTU assembly as set forth in claim 4 wherein lengths of discrete third and fourth wires (74,76) extend from said MTU circuit unit (60,290) of said first section (40) to comprise said conductors for electrically connecting said MTU circuit unit (60,290) to respective ones of said pair of binding posts (20,22).

6. An add-on MTU assembly as set forth in claim 4 wherein said second module (100) includes an annular cavity (120) about a center post (124) , and said first and second terminals (112,114) are cylindrical and are inserted into said annular cavity (120) and insulatively separated from each other, wire-receiving apertures

(106,108) extend into said second module (100) aligned with wire-receiving holes (160) of respective ones of said first and second terminals (112,114), and an actuator member (110) is rotatable to rotate said cylindrically shaped first and second terminals to become electrically connected with ends of tip and ring subscriber wires

(24,26) inserted fully into said wire-receiving apertures (106,108) and said wire-receiving holes (160), thus interconnecting said tip and ring subscriber wires (24,26) with said MTU circuit unit (60,290).

7. An add-on MTU assembly as set forth in claim 6 wherein said second module (100) includes a first and second passageways (134,136) extending thereinto from a bottom face (138) thereof, said first passageway (134) extends upwardly through said center post (124) to a top end (144) thereof, said second passageway (136) communicates with said annular cavity (120) at a bottom thereof, said center post (124) includes a groove (140,142) vertically along an outer surface thereof in communication with said annular cavity (120) and aligned with said second passageway (136) , said groove includes a lower portion (140) adjacent said cavity bottom and an upper portion (142) extending to said top end (144) of said center post (124) with a wall separating said upper and lower portions (140,142), and stripped end lengths of said first and second wires (70,72) are inserted into respective said passageways (134,136), with that of said first wire (70) inserted completely through said first passageway (134) and bent back into said annular cavity (120) and disposed along said upper groove portion (142) , and that of said second wire (72) extending into said annular cavity (120) and disposed along said lower groove portion (140) , for said stripped end lengths of said first and second wires (70,72) to be in electrical engagement with respective ones of said first and second terminals (112,114) inserted into said annular cavity (120) about said center post (124) .

8. An add-on MTU assembly (10) as set forth in claim 4 wherein a first said binding post clamp (44,264) is defined by said first module (40,250) to provide for clamping of said first module (40,250) to a respective said binding post of said pair (20,22) , and a second said binding post clamp (104,314) is defined by said second module (100,200,300) to provide for clamping of said second module (100,200,300) to a respective other said binding post of said pair (20,22).

9. An add-on MTU assembly (10) as set forth in claim 4 wherein said first module (40,250) defines a large interior cavity (46,298) extending thereinto from an insertion face (258) , and opposed interior end walls include opposed guide slots (296) for guided insertion and holding of a circuit card of said MTU circuit unit (60,290) into said cavity (46,298), and a cover member (266) is affixed to said insertion face (258) to enclose said cavity (46,298) to conclude assembly of said first module (40,250), and said first module (40,250) includes a test port (52,280) adjacent a selected one of said first and second conductors to permit testing of circuit integrity upon placement of the assembly (10) onto said binding post pair (20,22) .

10. An add-on MTU assembly (10) as set forth in claim 4 wherein said second module (300) comprises a pair of conductive shafts (302,304) having exposed shaft sections (306,308) extending from an insulative body (310) at least securely affixed thereto, and a said binding post clamp (314) affixed to said insulative body (310) , and said exposed shaft sections (306,308) are threaded and pairs of nuts (318) are disposed on respective said exposed shaft portions (306,308) enabling clamping to stripped ends of at least respective said subscriber tip and ring wires (24,26).